Removed nlohmann/json submodule

The submodule contained around 73MB of benchmarks and tests that are not necessary for inclusion in this project. Thus, the submodule has been removed, and the 2.0.7 release of nlohmann/json has been added to the repository.

4 files changed, 10795 insertions, 4 deletions

@@ -1,3 +0,0 @@
-[submodule "vendor/json"]
-        path = vendor/json
-        url = https://github.com/nlohmann/json
@@ -4,7 +4,7 @@ project (verbly)
 find_package(PkgConfig)
 pkg_check_modules(sqlite3 sqlite3>=3.8.3 REQUIRED)
 
-include_directories(vendor/json/src)
+include_directories(vendor/json)
 add_library(verbly lib/data.cpp lib/adjective.cpp lib/noun.cpp lib/verb.cpp lib/adverb.cpp lib/token.cpp lib/word.cpp lib/frame.cpp lib/preposition.cpp lib/adjective_query.cpp lib/adverb_query.cpp lib/noun_query.cpp lib/verb_query.cpp lib/frame_query.cpp)
 set_property(TARGET verbly PROPERTY CXX_STANDARD 11)
 set_property(TARGET verbly PROPERTY CXX_STANDARD_REQUIRED ON)
-Subproject 2b137110095c2b2046cde5af4ac8892b8a3f380
@@ -0,0 +1,10794 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++
+|  |  |__   |  |  | | | |  version 2.0.7
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#ifndef NLOHMANN_JSON_HPP
+#define NLOHMANN_JSON_HPP
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <cctype>
+#include <ciso646>
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <functional>
+#include <initializer_list>
+#include <iomanip>
+#include <iostream>
+#include <iterator>
+#include <limits>
+#include <locale>
+#include <map>
+#include <memory>
+#include <numeric>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+// exclude unsupported compilers
+#if defined(__clang__)
+    #define CLANG_VERSION (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__)
+    #if CLANG_VERSION < 30400
+        #error "unsupported Clang version - see https://github.com/nlohmann/json#supported-compilers"
+    #endif
+#elif defined(__GNUC__)
+    #define GCC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
+    #if GCC_VERSION < 40900
+        #error "unsupported GCC version - see https://github.com/nlohmann/json#supported-compilers"
+    #endif
+#endif
+
+// disable float-equal warnings on GCC/clang
+#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wfloat-equal"
+#endif
+
+// allow for portable deprecation warnings
+#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
+    #define JSON_DEPRECATED __attribute__((deprecated))
+#elif defined(_MSC_VER)
+    #define JSON_DEPRECATED __declspec(deprecated)
+#else
+    #define JSON_DEPRECATED
+#endif
+
+/*!
+@brief namespace for Niels Lohmann
+@see https://github.com/nlohmann
+@since version 1.0.0
+*/
+namespace nlohmann
+{
+
+
+/*!
+@brief unnamed namespace with internal helper functions
+@since version 1.0.0
+*/
+namespace
+{
+/*!
+@brief Helper to determine whether there's a key_type for T.
+
+Thus helper is used to tell associative containers apart from other containers
+such as sequence containers. For instance, `std::map` passes the test as it
+contains a `mapped_type`, whereas `std::vector` fails the test.
+
+@sa http://stackoverflow.com/a/7728728/266378
+@since version 1.0.0, overworked in version 2.0.6
+*/
+template<typename T>
+struct has_mapped_type
+{
+  private:
+    template <typename U, typename = typename U::mapped_type>
+    static int detect(U&&);
+
+    static void detect(...);
+  public:
+    static constexpr bool value =
+        std::is_integral<decltype(detect(std::declval<T>()))>::value;
+};
+
+/*!
+@brief helper class to create locales with decimal point
+
+This struct is used a default locale during the JSON serialization. JSON
+requires the decimal point to be `.`, so this function overloads the
+`do_decimal_point()` function to return `.`. This function is called by
+float-to-string conversions to retrieve the decimal separator between integer
+and fractional parts.
+
+@sa https://github.com/nlohmann/json/issues/51#issuecomment-86869315
+@since version 2.0.0
+*/
+struct DecimalSeparator : std::numpunct<char>
+{
+    char do_decimal_point() const
+    {
+        return '.';
+    }
+};
+
+}
+
+/*!
+@brief a class to store JSON values
+
+@tparam ObjectType type for JSON objects (`std::map` by default; will be used
+in @ref object_t)
+@tparam ArrayType type for JSON arrays (`std::vector` by default; will be used
+in @ref array_t)
+@tparam StringType type for JSON strings and object keys (`std::string` by
+default; will be used in @ref string_t)
+@tparam BooleanType type for JSON booleans (`bool` by default; will be used
+in @ref boolean_t)
+@tparam NumberIntegerType type for JSON integer numbers (`int64_t` by
+default; will be used in @ref number_integer_t)
+@tparam NumberUnsignedType type for JSON unsigned integer numbers (@c
+`uint64_t` by default; will be used in @ref number_unsigned_t)
+@tparam NumberFloatType type for JSON floating-point numbers (`double` by
+default; will be used in @ref number_float_t)
+@tparam AllocatorType type of the allocator to use (`std::allocator` by
+default)
+
+@requirement The class satisfies the following concept requirements:
+- Basic
+ - [DefaultConstructible](http://en.cppreference.com/w/cpp/concept/DefaultConstructible):
+   JSON values can be default constructed. The result will be a JSON null value.
+ - [MoveConstructible](http://en.cppreference.com/w/cpp/concept/MoveConstructible):
+   A JSON value can be constructed from an rvalue argument.
+ - [CopyConstructible](http://en.cppreference.com/w/cpp/concept/CopyConstructible):
+   A JSON value can be copy-constructed from an lvalue expression.
+ - [MoveAssignable](http://en.cppreference.com/w/cpp/concept/MoveAssignable):
+   A JSON value van be assigned from an rvalue argument.
+ - [CopyAssignable](http://en.cppreference.com/w/cpp/concept/CopyAssignable):
+   A JSON value can be copy-assigned from an lvalue expression.
+ - [Destructible](http://en.cppreference.com/w/cpp/concept/Destructible):
+   JSON values can be destructed.
+- Layout
+ - [StandardLayoutType](http://en.cppreference.com/w/cpp/concept/StandardLayoutType):
+   JSON values have
+   [standard layout](http://en.cppreference.com/w/cpp/language/data_members#Standard_layout):
+   All non-static data members are private and standard layout types, the class
+   has no virtual functions or (virtual) base classes.
+- Library-wide
+ - [EqualityComparable](http://en.cppreference.com/w/cpp/concept/EqualityComparable):
+   JSON values can be compared with `==`, see @ref
+   operator==(const_reference,const_reference).
+ - [LessThanComparable](http://en.cppreference.com/w/cpp/concept/LessThanComparable):
+   JSON values can be compared with `<`, see @ref
+   operator<(const_reference,const_reference).
+ - [Swappable](http://en.cppreference.com/w/cpp/concept/Swappable):
+   Any JSON lvalue or rvalue of can be swapped with any lvalue or rvalue of
+   other compatible types, using unqualified function call @ref swap().
+ - [NullablePointer](http://en.cppreference.com/w/cpp/concept/NullablePointer):
+   JSON values can be compared against `std::nullptr_t` objects which are used
+   to model the `null` value.
+- Container
+ - [Container](http://en.cppreference.com/w/cpp/concept/Container):
+   JSON values can be used like STL containers and provide iterator access.
+ - [ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer);
+   JSON values can be used like STL containers and provide reverse iterator
+   access.
+
+@invariant The member variables @a m_value and @a m_type have the following
+relationship:
+- If `m_type == value_t::object`, then `m_value.object != nullptr`.
+- If `m_type == value_t::array`, then `m_value.array != nullptr`.
+- If `m_type == value_t::string`, then `m_value.string != nullptr`.
+The invariants are checked by member function assert_invariant().
+
+@internal
+@note ObjectType trick from http://stackoverflow.com/a/9860911
+@endinternal
+
+@see [RFC 7159: The JavaScript Object Notation (JSON) Data Interchange
+Format](http://rfc7159.net/rfc7159)
+
+@since version 1.0.0
+
+@nosubgrouping
+*/
+template <
+    template<typename U, typename V, typename... Args> class ObjectType = std::map,
+    template<typename U, typename... Args> class ArrayType = std::vector,
+    class StringType = std::string,
+    class BooleanType = bool,
+    class NumberIntegerType = std::int64_t,
+    class NumberUnsignedType = std::uint64_t,
+    class NumberFloatType = double,
+    template<typename U> class AllocatorType = std::allocator
+    >
+class basic_json
+{
+  private:
+    /// workaround type for MSVC
+    using basic_json_t = basic_json<ObjectType, ArrayType, StringType,
+          BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType,
+          AllocatorType>;
+
+  public:
+    // forward declarations
+    template<typename Base> class json_reverse_iterator;
+    class json_pointer;
+
+    /////////////////////
+    // container types //
+    /////////////////////
+
+    /// @name container types
+    /// The canonic container types to use @ref basic_json like any other STL
+    /// container.
+    /// @{
+
+    /// the type of elements in a basic_json container
+    using value_type = basic_json;
+
+    /// the type of an element reference
+    using reference = value_type&;
+    /// the type of an element const reference
+    using const_reference = const value_type&;
+
+    /// a type to represent differences between iterators
+    using difference_type = std::ptrdiff_t;
+    /// a type to represent container sizes
+    using size_type = std::size_t;
+
+    /// the allocator type
+    using allocator_type = AllocatorType<basic_json>;
+
+    /// the type of an element pointer
+    using pointer = typename std::allocator_traits<allocator_type>::pointer;
+    /// the type of an element const pointer
+    using const_pointer = typename std::allocator_traits<allocator_type>::const_pointer;
+
+    /// an iterator for a basic_json container
+    class iterator;
+    /// a const iterator for a basic_json container
+    class const_iterator;
+    /// a reverse iterator for a basic_json container
+    using reverse_iterator = json_reverse_iterator<typename basic_json::iterator>;
+    /// a const reverse iterator for a basic_json container
+    using const_reverse_iterator = json_reverse_iterator<typename basic_json::const_iterator>;
+
+    /// @}
+
+
+    /*!
+    @brief returns the allocator associated with the container
+    */
+    static allocator_type get_allocator()
+    {
+        return allocator_type();
+    }
+
+
+    ///////////////////////////
+    // JSON value data types //
+    ///////////////////////////
+
+    /// @name JSON value data types
+    /// The data types to store a JSON value. These types are derived from
+    /// the template arguments passed to class @ref basic_json.
+    /// @{
+
+    /*!
+    @brief a type for an object
+
+    [RFC 7159](http://rfc7159.net/rfc7159) describes JSON objects as follows:
+    > An object is an unordered collection of zero or more name/value pairs,
+    > where a name is a string and a value is a string, number, boolean, null,
+    > object, or array.
+
+    To store objects in C++, a type is defined by the template parameters
+    described below.
+
+    @tparam ObjectType  the container to store objects (e.g., `std::map` or
+    `std::unordered_map`)
+    @tparam StringType the type of the keys or names (e.g., `std::string`).
+    The comparison function `std::less<StringType>` is used to order elements
+    inside the container.
+    @tparam AllocatorType the allocator to use for objects (e.g.,
+    `std::allocator`)
+
+    #### Default type
+
+    With the default values for @a ObjectType (`std::map`), @a StringType
+    (`std::string`), and @a AllocatorType (`std::allocator`), the default
+    value for @a object_t is:
+
+    @code {.cpp}
+    std::map<
+      std::string, // key_type
+      basic_json, // value_type
+      std::less<std::string>, // key_compare
+      std::allocator<std::pair<const std::string, basic_json>> // allocator_type
+    >
+    @endcode
+
+    #### Behavior
+
+    The choice of @a object_t influences the behavior of the JSON class. With
+    the default type, objects have the following behavior:
+
+    - When all names are unique, objects will be interoperable in the sense
+      that all software implementations receiving that object will agree on
+      the name-value mappings.
+    - When the names within an object are not unique, later stored name/value
+      pairs overwrite previously stored name/value pairs, leaving the used
+      names unique. For instance, `{"key": 1}` and `{"key": 2, "key": 1}` will
+      be treated as equal and both stored as `{"key": 1}`.
+    - Internally, name/value pairs are stored in lexicographical order of the
+      names. Objects will also be serialized (see @ref dump) in this order.
+      For instance, `{"b": 1, "a": 2}` and `{"a": 2, "b": 1}` will be stored
+      and serialized as `{"a": 2, "b": 1}`.
+    - When comparing objects, the order of the name/value pairs is irrelevant.
+      This makes objects interoperable in the sense that they will not be
+      affected by these differences. For instance, `{"b": 1, "a": 2}` and
+      `{"a": 2, "b": 1}` will be treated as equal.
+
+    #### Limits
+
+    [RFC 7159](http://rfc7159.net/rfc7159) specifies:
+    > An implementation may set limits on the maximum depth of nesting.
+
+    In this class, the object's limit of nesting is not constraint explicitly.
+    However, a maximum depth of nesting may be introduced by the compiler or
+    runtime environment. A theoretical limit can be queried by calling the
+    @ref max_size function of a JSON object.
+
+    #### Storage
+
+    Objects are stored as pointers in a @ref basic_json type. That is, for any
+    access to object values, a pointer of type `object_t*` must be
+    dereferenced.
+
+    @sa @ref array_t -- type for an array value
+
+    @since version 1.0.0
+
+    @note The order name/value pairs are added to the object is *not*
+    preserved by the library. Therefore, iterating an object may return
+    name/value pairs in a different order than they were originally stored. In
+    fact, keys will be traversed in alphabetical order as `std::map` with
+    `std::less` is used by default. Please note this behavior conforms to [RFC
+    7159](http://rfc7159.net/rfc7159), because any order implements the
+    specified "unordered" nature of JSON objects.
+    */
+    using object_t = ObjectType<StringType,
+          basic_json,
+          std::less<StringType>,
+          AllocatorType<std::pair<const StringType,
+          basic_json>>>;
+
+    /*!
+    @brief a type for an array
+
+    [RFC 7159](http://rfc7159.net/rfc7159) describes JSON arrays as follows:
+    > An array is an ordered sequence of zero or more values.
+
+    To store objects in C++, a type is defined by the template parameters
+    explained below.
+
+    @tparam ArrayType  container type to store arrays (e.g., `std::vector` or
+    `std::list`)
+    @tparam AllocatorType allocator to use for arrays (e.g., `std::allocator`)
+
+    #### Default type
+
+    With the default values for @a ArrayType (`std::vector`) and @a
+    AllocatorType (`std::allocator`), the default value for @a array_t is:
+
+    @code {.cpp}
+    std::vector<
+      basic_json, // value_type
+      std::allocator<basic_json> // allocator_type
+    >
+    @endcode
+
+    #### Limits
+
+    [RFC 7159](http://rfc7159.net/rfc7159) specifies:
+    > An implementation may set limits on the maximum depth of nesting.
+
+    In this class, the array's limit of nesting is not constraint explicitly.
+    However, a maximum depth of nesting may be introduced by the compiler or
+    runtime environment. A theoretical limit can be queried by calling the
+    @ref max_size function of a JSON array.
+
+    #### Storage
+
+    Arrays are stored as pointers in a @ref basic_json type. That is, for any
+    access to array values, a pointer of type `array_t*` must be dereferenced.
+
+    @sa @ref object_t -- type for an object value
+
+    @since version 1.0.0
+    */
+    using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
+
+    /*!
+    @brief a type for a string
+
+    [RFC 7159](http://rfc7159.net/rfc7159) describes JSON strings as follows:
+    > A string is a sequence of zero or more Unicode characters.
+
+    To store objects in C++, a type is defined by the template parameter
+    described below. Unicode values are split by the JSON class into
+    byte-sized characters during deserialization.
+
+    @tparam StringType  the container to store strings (e.g., `std::string`).
+    Note this container is used for keys/names in objects, see @ref object_t.
+
+    #### Default type
+
+    With the default values for @a StringType (`std::string`), the default
+    value for @a string_t is:
+
+    @code {.cpp}
+    std::string
+    @endcode
+
+    #### String comparison
+
+    [RFC 7159](http://rfc7159.net/rfc7159) states:
+    > Software implementations are typically required to test names of object
+    > members for equality. Implementations that transform the textual
+    > representation into sequences of Unicode code units and then perform the
+    > comparison numerically, code unit by code unit, are interoperable in the
+    > sense that implementations will agree in all cases on equality or
+    > inequality of two strings. For example, implementations that compare
+    > strings with escaped characters unconverted may incorrectly find that
+    > `"a\\b"` and `"a\u005Cb"` are not equal.
+
+    This implementation is interoperable as it does compare strings code unit
+    by code unit.
+
+    #### Storage
+
+    String values are stored as pointers in a @ref basic_json type. That is,
+    for any access to string values, a pointer of type `string_t*` must be
+    dereferenced.
+
+    @since version 1.0.0
+    */
+    using string_t = StringType;
+
+    /*!
+    @brief a type for a boolean
+
+    [RFC 7159](http://rfc7159.net/rfc7159) implicitly describes a boolean as a
+    type which differentiates the two literals `true` and `false`.
+
+    To store objects in C++, a type is defined by the template parameter @a
+    BooleanType which chooses the type to use.
+
+    #### Default type
+
+    With the default values for @a BooleanType (`bool`), the default value for
+    @a boolean_t is:
+
+    @code {.cpp}
+    bool
+    @endcode
+
+    #### Storage
+
+    Boolean values are stored directly inside a @ref basic_json type.
+
+    @since version 1.0.0
+    */
+    using boolean_t = BooleanType;
+
+    /*!
+    @brief a type for a number (integer)
+
+    [RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
+    > The representation of numbers is similar to that used in most
+    > programming languages. A number is represented in base 10 using decimal
+    > digits. It contains an integer component that may be prefixed with an
+    > optional minus sign, which may be followed by a fraction part and/or an
+    > exponent part. Leading zeros are not allowed. (...) Numeric values that
+    > cannot be represented in the grammar below (such as Infinity and NaN)
+    > are not permitted.
+
+    This description includes both integer and floating-point numbers.
+    However, C++ allows more precise storage if it is known whether the number
+    is a signed integer, an unsigned integer or a floating-point number.
+    Therefore, three different types, @ref number_integer_t, @ref
+    number_unsigned_t and @ref number_float_t are used.
+
+    To store integer numbers in C++, a type is defined by the template
+    parameter @a NumberIntegerType which chooses the type to use.
+
+    #### Default type
+
+    With the default values for @a NumberIntegerType (`int64_t`), the default
+    value for @a number_integer_t is:
+
+    @code {.cpp}
+    int64_t
+    @endcode
+
+    #### Default behavior
+
+    - The restrictions about leading zeros is not enforced in C++. Instead,
+      leading zeros in integer literals lead to an interpretation as octal
+      number. Internally, the value will be stored as decimal number. For
+      instance, the C++ integer literal `010` will be serialized to `8`.
+      During deserialization, leading zeros yield an error.
+    - Not-a-number (NaN) values will be serialized to `null`.
+
+    #### Limits
+
+    [RFC 7159](http://rfc7159.net/rfc7159) specifies:
+    > An implementation may set limits on the range and precision of numbers.
+
+    When the default type is used, the maximal integer number that can be
+    stored is `9223372036854775807` (INT64_MAX) and the minimal integer number
+    that can be stored is `-9223372036854775808` (INT64_MIN). Integer numbers
+    that are out of range will yield over/underflow when used in a
+    constructor. During deserialization, too large or small integer numbers
+    will be automatically be stored as @ref number_unsigned_t or @ref
+    number_float_t.
+
+    [RFC 7159](http://rfc7159.net/rfc7159) further states:
+    > Note that when such software is used, numbers that are integers and are
+    > in the range \f$[-2^{53}+1, 2^{53}-1]\f$ are interoperable in the sense
+    > that implementations will agree exactly on their numeric values.
+
+    As this range is a subrange of the exactly supported range [INT64_MIN,
+    INT64_MAX], this class's integer type is interoperable.
+
+    #### Storage
+
+    Integer number values are stored directly inside a @ref basic_json type.
+
+    @sa @ref number_float_t -- type for number values (floating-point)
+
+    @sa @ref number_unsigned_t -- type for number values (unsigned integer)
+
+    @since version 1.0.0
+    */
+    using number_integer_t = NumberIntegerType;
+
+    /*!
+    @brief a type for a number (unsigned)
+
+    [RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
+    > The representation of numbers is similar to that used in most
+    > programming languages. A number is represented in base 10 using decimal
+    > digits. It contains an integer component that may be prefixed with an
+    > optional minus sign, which may be followed by a fraction part and/or an
+    > exponent part. Leading zeros are not allowed. (...) Numeric values that
+    > cannot be represented in the grammar below (such as Infinity and NaN)
+    > are not permitted.
+
+    This description includes both integer and floating-point numbers.
+    However, C++ allows more precise storage if it is known whether the number
+    is a signed integer, an unsigned integer or a floating-point number.
+    Therefore, three different types, @ref number_integer_t, @ref
+    number_unsigned_t and @ref number_float_t are used.
+
+    To store unsigned integer numbers in C++, a type is defined by the
+    template parameter @a NumberUnsignedType which chooses the type to use.
+
+    #### Default type
+
+    With the default values for @a NumberUnsignedType (`uint64_t`), the
+    default value for @a number_unsigned_t is:
+
+    @code {.cpp}
+    uint64_t
+    @endcode
+
+    #### Default behavior
+
+    - The restrictions about leading zeros is not enforced in C++. Instead,
+      leading zeros in integer literals lead to an interpretation as octal
+      number. Internally, the value will be stored as decimal number. For
+      instance, the C++ integer literal `010` will be serialized to `8`.
+      During deserialization, leading zeros yield an error.
+    - Not-a-number (NaN) values will be serialized to `null`.
+
+    #### Limits
+
+    [RFC 7159](http://rfc7159.net/rfc7159) specifies:
+    > An implementation may set limits on the range and precision of numbers.
+
+    When the default type is used, the maximal integer number that can be
+    stored is `18446744073709551615` (UINT64_MAX) and the minimal integer
+    number that can be stored is `0`. Integer numbers that are out of range
+    will yield over/underflow when used in a constructor. During
+    deserialization, too large or small integer numbers will be automatically
+    be stored as @ref number_integer_t or @ref number_float_t.
+
+    [RFC 7159](http://rfc7159.net/rfc7159) further states:
+    > Note that when such software is used, numbers that are integers and are
+    > in the range \f$[-2^{53}+1, 2^{53}-1]\f$ are interoperable in the sense
+    > that implementations will agree exactly on their numeric values.
+
+    As this range is a subrange (when considered in conjunction with the
+    number_integer_t type) of the exactly supported range [0, UINT64_MAX],
+    this class's integer type is interoperable.
+
+    #### Storage
+
+    Integer number values are stored directly inside a @ref basic_json type.
+
+    @sa @ref number_float_t -- type for number values (floating-point)
+    @sa @ref number_integer_t -- type for number values (integer)
+
+    @since version 2.0.0
+    */
+    using number_unsigned_t = NumberUnsignedType;
+
+    /*!
+    @brief a type for a number (floating-point)
+
+    [RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
+    > The representation of numbers is similar to that used in most
+    > programming languages. A number is represented in base 10 using decimal
+    > digits. It contains an integer component that may be prefixed with an
+    > optional minus sign, which may be followed by a fraction part and/or an
+    > exponent part. Leading zeros are not allowed. (...) Numeric values that
+    > cannot be represented in the grammar below (such as Infinity and NaN)
+    > are not permitted.
+
+    This description includes both integer and floating-point numbers.
+    However, C++ allows more precise storage if it is known whether the number
+    is a signed integer, an unsigned integer or a floating-point number.
+    Therefore, three different types, @ref number_integer_t, @ref
+    number_unsigned_t and @ref number_float_t are used.
+
+    To store floating-point numbers in C++, a type is defined by the template
+    parameter @a NumberFloatType which chooses the type to use.
+
+    #### Default type
+
+    With the default values for @a NumberFloatType (`double`), the default
+    value for @a number_float_t is:
+
+    @code {.cpp}
+    double
+    @endcode
+
+    #### Default behavior
+
+    - The restrictions about leading zeros is not enforced in C++. Instead,
+      leading zeros in floating-point literals will be ignored. Internally,
+      the value will be stored as decimal number. For instance, the C++
+      floating-point literal `01.2` will be serialized to `1.2`. During
+      deserialization, leading zeros yield an error.
+    - Not-a-number (NaN) values will be serialized to `null`.
+
+    #### Limits
+
+    [RFC 7159](http://rfc7159.net/rfc7159) states:
+    > This specification allows implementations to set limits on the range and
+    > precision of numbers accepted. Since software that implements IEEE
+    > 754-2008 binary64 (double precision) numbers is generally available and
+    > widely used, good interoperability can be achieved by implementations
+    > that expect no more precision or range than these provide, in the sense
+    > that implementations will approximate JSON numbers within the expected
+    > precision.
+
+    This implementation does exactly follow this approach, as it uses double
+    precision floating-point numbers. Note values smaller than
+    `-1.79769313486232e+308` and values greater than `1.79769313486232e+308`
+    will be stored as NaN internally and be serialized to `null`.
+
+    #### Storage
+
+    Floating-point number values are stored directly inside a @ref basic_json
+    type.
+
+    @sa @ref number_integer_t -- type for number values (integer)
+
+    @sa @ref number_unsigned_t -- type for number values (unsigned integer)
+
+    @since version 1.0.0
+    */
+    using number_float_t = NumberFloatType;
+
+    /// @}
+
+
+    ///////////////////////////
+    // JSON type enumeration //
+    ///////////////////////////
+
+    /*!
+    @brief the JSON type enumeration
+
+    This enumeration collects the different JSON types. It is internally used
+    to distinguish the stored values, and the functions @ref is_null(), @ref
+    is_object(), @ref is_array(), @ref is_string(), @ref is_boolean(), @ref
+    is_number() (with @ref is_number_integer(), @ref is_number_unsigned(), and
+    @ref is_number_float()), @ref is_discarded(), @ref is_primitive(), and
+    @ref is_structured() rely on it.
+
+    @note There are three enumeration entries (number_integer,
+    number_unsigned, and number_float), because the library distinguishes
+    these three types for numbers: @ref number_unsigned_t is used for unsigned
+    integers, @ref number_integer_t is used for signed integers, and @ref
+    number_float_t is used for floating-point numbers or to approximate
+    integers which do not fit in the limits of their respective type.
+
+    @sa @ref basic_json(const value_t value_type) -- create a JSON value with
+    the default value for a given type
+
+    @since version 1.0.0
+    */
+    enum class value_t : uint8_t
+    {
+        null,            ///< null value
+        object,          ///< object (unordered set of name/value pairs)
+        array,           ///< array (ordered collection of values)
+        string,          ///< string value
+        boolean,         ///< boolean value
+        number_integer,  ///< number value (signed integer)
+        number_unsigned, ///< number value (unsigned integer)
+        number_float,    ///< number value (floating-point)
+        discarded        ///< discarded by the the parser callback function
+    };
+
+
+  private:
+
+    /// helper for exception-safe object creation
+    template<typename T, typename... Args>
+    static T* create(Args&& ... args)
+    {
+        AllocatorType<T> alloc;
+        auto deleter = [&](T * object)
+        {
+            alloc.deallocate(object, 1);
+        };
+        std::unique_ptr<T, decltype(deleter)> object(alloc.allocate(1), deleter);
+        alloc.construct(object.get(), std::forward<Args>(args)...);
+        assert(object.get() != nullptr);
+        return object.release();
+    }
+
+    ////////////////////////
+    // JSON value storage //
+    ////////////////////////
+
+    /*!
+    @brief a JSON value
+
+    The actual storage for a JSON value of the @ref basic_json class. This
+    union combines the different storage types for the JSON value types
+    defined in @ref value_t.
+
+    JSON type | value_t type    | used type
+    --------- | --------------- | ------------------------
+    object    | object          | pointer to @ref object_t
+    array     | array           | pointer to @ref array_t
+    string    | string          | pointer to @ref string_t
+    boolean   | boolean         | @ref boolean_t
+    number    | number_integer  | @ref number_integer_t
+    number    | number_unsigned | @ref number_unsigned_t
+    number    | number_float    | @ref number_float_t
+    null      | null            | *no value is stored*
+
+    @note Variable-length types (objects, arrays, and strings) are stored as
+    pointers. The size of the union should not exceed 64 bits if the default
+    value types are used.
+
+    @since version 1.0.0
+    */
+    union json_value
+    {
+        /// object (stored with pointer to save storage)
+        object_t* object;
+        /// array (stored with pointer to save storage)
+        array_t* array;
+        /// string (stored with pointer to save storage)
+        string_t* string;
+        /// boolean
+        boolean_t boolean;
+        /// number (integer)
+        number_integer_t number_integer;
+        /// number (unsigned integer)
+        number_unsigned_t number_unsigned;
+        /// number (floating-point)
+        number_float_t number_float;
+
+        /// default constructor (for null values)
+        json_value() = default;
+        /// constructor for booleans
+        json_value(boolean_t v) noexcept : boolean(v) {}
+        /// constructor for numbers (integer)
+        json_value(number_integer_t v) noexcept : number_integer(v) {}
+        /// constructor for numbers (unsigned)
+        json_value(number_unsigned_t v) noexcept : number_unsigned(v) {}
+        /// constructor for numbers (floating-point)
+        json_value(number_float_t v) noexcept : number_float(v) {}
+        /// constructor for empty values of a given type
+        json_value(value_t t)
+        {
+            switch (t)
+            {
+                case value_t::object:
+                {
+                    object = create<object_t>();
+                    break;
+                }
+
+                case value_t::array:
+                {
+                    array = create<array_t>();
+                    break;
+                }
+
+                case value_t::string:
+                {
+                    string = create<string_t>("");
+                    break;
+                }
+
+                case value_t::boolean:
+                {
+                    boolean = boolean_t(false);
+                    break;
+                }
+
+                case value_t::number_integer:
+                {
+                    number_integer = number_integer_t(0);
+                    break;
+                }
+
+                case value_t::number_unsigned:
+                {
+                    number_unsigned = number_unsigned_t(0);
+                    break;
+                }
+
+                case value_t::number_float:
+                {
+                    number_float = number_float_t(0.0);
+                    break;
+                }
+
+                default:
+                {
+                    break;
+                }
+            }
+        }
+
+        /// constructor for strings
+        json_value(const string_t& value)
+        {
+            string = create<string_t>(value);
+        }
+
+        /// constructor for objects
+        json_value(const object_t& value)
+        {
+            object = create<object_t>(value);
+        }
+
+        /// constructor for arrays
+        json_value(const array_t& value)
+        {
+            array = create<array_t>(value);
+        }
+    };
+
+    /*!
+    @brief checks the class invariants
+
+    This function asserts the class invariants. It needs to be called at the
+    end of every constructor to make sure that created objects respect the
+    invariant. Furthermore, it has to be called each time the type of a JSON
+    value is changed, because the invariant expresses a relationship between
+    @a m_type and @a m_value.
+    */
+    void assert_invariant() const
+    {
+        assert(m_type != value_t::object or m_value.object != nullptr);
+        assert(m_type != value_t::array or m_value.array != nullptr);
+        assert(m_type != value_t::string or m_value.string != nullptr);
+    }
+
+  public:
+    //////////////////////////
+    // JSON parser callback //
+    //////////////////////////
+
+    /*!
+    @brief JSON callback events
+
+    This enumeration lists the parser events that can trigger calling a
+    callback function of type @ref parser_callback_t during parsing.
+
+    @image html callback_events.png "Example when certain parse events are triggered"
+
+    @since version 1.0.0
+    */
+    enum class parse_event_t : uint8_t
+    {
+        /// the parser read `{` and started to process a JSON object
+        object_start,
+        /// the parser read `}` and finished processing a JSON object
+        object_end,
+        /// the parser read `[` and started to process a JSON array
+        array_start,
+        /// the parser read `]` and finished processing a JSON array
+        array_end,
+        /// the parser read a key of a value in an object
+        key,
+        /// the parser finished reading a JSON value
+        value
+    };
+
+    /*!
+    @brief per-element parser callback type
+
+    With a parser callback function, the result of parsing a JSON text can be
+    influenced. When passed to @ref parse(std::istream&, const
+    parser_callback_t) or @ref parse(const char*, const parser_callback_t),
+    it is called on certain events (passed as @ref parse_event_t via parameter
+    @a event) with a set recursion depth @a depth and context JSON value
+    @a parsed. The return value of the callback function is a boolean
+    indicating whether the element that emitted the callback shall be kept or
+    not.
+
+    We distinguish six scenarios (determined by the event type) in which the
+    callback function can be called. The following table describes the values
+    of the parameters @a depth, @a event, and @a parsed.
+
+    parameter @a event | description | parameter @a depth | parameter @a parsed
+    ------------------ | ----------- | ------------------ | -------------------
+    parse_event_t::object_start | the parser read `{` and started to process a JSON object | depth of the parent of the JSON object | a JSON value with type discarded
+    parse_event_t::key | the parser read a key of a value in an object | depth of the currently parsed JSON object | a JSON string containing the key
+    parse_event_t::object_end | the parser read `}` and finished processing a JSON object | depth of the parent of the JSON object | the parsed JSON object
+    parse_event_t::array_start | the parser read `[` and started to process a JSON array | depth of the parent of the JSON array | a JSON value with type discarded
+    parse_event_t::array_end | the parser read `]` and finished processing a JSON array | depth of the parent of the JSON array | the parsed JSON array
+    parse_event_t::value | the parser finished reading a JSON value | depth of the value | the parsed JSON value
+
+    @image html callback_events.png "Example when certain parse events are triggered"
+
+    Discarding a value (i.e., returning `false`) has different effects
+    depending on the context in which function was called:
+
+    - Discarded values in structured types are skipped. That is, the parser
+      will behave as if the discarded value was never read.
+    - In case a value outside a structured type is skipped, it is replaced
+      with `null`. This case happens if the top-level element is skipped.
+
+    @param[in] depth  the depth of the recursion during parsing
+
+    @param[in] event  an event of type parse_event_t indicating the context in
+    the callback function has been called
+
+    @param[in,out] parsed  the current intermediate parse result; note that
+    writing to this value has no effect for parse_event_t::key events
+
+    @return Whether the JSON value which called the function during parsing
+    should be kept (`true`) or not (`false`). In the latter case, it is either
+    skipped completely or replaced by an empty discarded object.
+
+    @sa @ref parse(std::istream&, parser_callback_t) or
+    @ref parse(const char*, parser_callback_t) for examples
+
+    @since version 1.0.0
+    */
+    using parser_callback_t = std::function<bool(int depth,
+                              parse_event_t event,
+                              basic_json& parsed)>;
+
+
+    //////////////////
+    // constructors //
+    //////////////////
+
+    /// @name constructors and destructors
+    /// Constructors of class @ref basic_json, copy/move constructor, copy
+    /// assignment, static functions creating objects, and the destructor.
+    /// @{
+
+    /*!
+    @brief create an empty value with a given type
+
+    Create an empty JSON value with a given type. The value will be default
+    initialized with an empty value which depends on the type:
+
+    Value type  | initial value
+    ----------- | -------------
+    null        | `null`
+    boolean     | `false`
+    string      | `""`
+    number      | `0`
+    object      | `{}`
+    array       | `[]`
+
+    @param[in] value_type  the type of the value to create
+
+    @complexity Constant.
+
+    @throw std::bad_alloc if allocation for object, array, or string value
+    fails
+
+    @liveexample{The following code shows the constructor for different @ref
+    value_t values,basic_json__value_t}
+
+    @sa @ref basic_json(std::nullptr_t) -- create a `null` value
+    @sa @ref basic_json(boolean_t value) -- create a boolean value
+    @sa @ref basic_json(const string_t&) -- create a string value
+    @sa @ref basic_json(const object_t&) -- create a object value
+    @sa @ref basic_json(const array_t&) -- create a array value
+    @sa @ref basic_json(const number_float_t) -- create a number
+    (floating-point) value
+    @sa @ref basic_json(const number_integer_t) -- create a number (integer)
+    value
+    @sa @ref basic_json(const number_unsigned_t) -- create a number (unsigned)
+    value
+
+    @since version 1.0.0
+    */
+    basic_json(const value_t value_type)
+        : m_type(value_type), m_value(value_type)
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create a null object
+
+    Create a `null` JSON value. It either takes a null pointer as parameter
+    (explicitly creating `null`) or no parameter (implicitly creating `null`).
+    The passed null pointer itself is not read -- it is only used to choose
+    the right constructor.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this constructor never throws
+    exceptions.
+
+    @liveexample{The following code shows the constructor with and without a
+    null pointer parameter.,basic_json__nullptr_t}
+
+    @since version 1.0.0
+    */
+    basic_json(std::nullptr_t = nullptr) noexcept
+        : basic_json(value_t::null)
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an object (explicit)
+
+    Create an object JSON value with a given content.
+
+    @param[in] val  a value for the object
+
+    @complexity Linear in the size of the passed @a val.
+
+    @throw std::bad_alloc if allocation for object value fails
+
+    @liveexample{The following code shows the constructor with an @ref
+    object_t parameter.,basic_json__object_t}
+
+    @sa @ref basic_json(const CompatibleObjectType&) -- create an object value
+    from a compatible STL container
+
+    @since version 1.0.0
+    */
+    basic_json(const object_t& val)
+        : m_type(value_t::object), m_value(val)
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an object (implicit)
+
+    Create an object JSON value with a given content. This constructor allows
+    any type @a CompatibleObjectType that can be used to construct values of
+    type @ref object_t.
+
+    @tparam CompatibleObjectType An object type whose `key_type` and
+    `value_type` is compatible to @ref object_t. Examples include `std::map`,
+    `std::unordered_map`, `std::multimap`, and `std::unordered_multimap` with
+    a `key_type` of `std::string`, and a `value_type` from which a @ref
+    basic_json value can be constructed.
+
+    @param[in] val  a value for the object
+
+    @complexity Linear in the size of the passed @a val.
+
+    @throw std::bad_alloc if allocation for object value fails
+
+    @liveexample{The following code shows the constructor with several
+    compatible object type parameters.,basic_json__CompatibleObjectType}
+
+    @sa @ref basic_json(const object_t&) -- create an object value
+
+    @since version 1.0.0
+    */
+    template<class CompatibleObjectType, typename std::enable_if<
+                 std::is_constructible<typename object_t::key_type, typename CompatibleObjectType::key_type>::value and
+                 std::is_constructible<basic_json, typename CompatibleObjectType::mapped_type>::value, int>::type = 0>
+    basic_json(const CompatibleObjectType& val)
+        : m_type(value_t::object)
+    {
+        using std::begin;
+        using std::end;
+        m_value.object = create<object_t>(begin(val), end(val));
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an array (explicit)
+
+    Create an array JSON value with a given content.
+
+    @param[in] val  a value for the array
+
+    @complexity Linear in the size of the passed @a val.
+
+    @throw std::bad_alloc if allocation for array value fails
+
+    @liveexample{The following code shows the constructor with an @ref array_t
+    parameter.,basic_json__array_t}
+
+    @sa @ref basic_json(const CompatibleArrayType&) -- create an array value
+    from a compatible STL containers
+
+    @since version 1.0.0
+    */
+    basic_json(const array_t& val)
+        : m_type(value_t::array), m_value(val)
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an array (implicit)
+
+    Create an array JSON value with a given content. This constructor allows
+    any type @a CompatibleArrayType that can be used to construct values of
+    type @ref array_t.
+
+    @tparam CompatibleArrayType An object type whose `value_type` is
+    compatible to @ref array_t. Examples include `std::vector`, `std::deque`,
+    `std::list`, `std::forward_list`, `std::array`, `std::set`,
+    `std::unordered_set`, `std::multiset`, and `unordered_multiset` with a
+    `value_type` from which a @ref basic_json value can be constructed.
+
+    @param[in] val  a value for the array
+
+    @complexity Linear in the size of the passed @a val.
+
+    @throw std::bad_alloc if allocation for array value fails
+
+    @liveexample{The following code shows the constructor with several
+    compatible array type parameters.,basic_json__CompatibleArrayType}
+
+    @sa @ref basic_json(const array_t&) -- create an array value
+
+    @since version 1.0.0
+    */
+    template<class CompatibleArrayType, typename std::enable_if<
+                 not std::is_same<CompatibleArrayType, typename basic_json_t::iterator>::value and
+                 not std::is_same<CompatibleArrayType, typename basic_json_t::const_iterator>::value and
+                 not std::is_same<CompatibleArrayType, typename basic_json_t::reverse_iterator>::value and
+                 not std::is_same<CompatibleArrayType, typename basic_json_t::const_reverse_iterator>::value and
+                 not std::is_same<CompatibleArrayType, typename array_t::iterator>::value and
+                 not std::is_same<CompatibleArrayType, typename array_t::const_iterator>::value and
+                 std::is_constructible<basic_json, typename CompatibleArrayType::value_type>::value, int>::type = 0>
+    basic_json(const CompatibleArrayType& val)
+        : m_type(value_t::array)
+    {
+        using std::begin;
+        using std::end;
+        m_value.array = create<array_t>(begin(val), end(val));
+        assert_invariant();
+    }
+
+    /*!
+    @brief create a string (explicit)
+
+    Create an string JSON value with a given content.
+
+    @param[in] val  a value for the string
+
+    @complexity Linear in the size of the passed @a val.
+
+    @throw std::bad_alloc if allocation for string value fails
+
+    @liveexample{The following code shows the constructor with an @ref
+    string_t parameter.,basic_json__string_t}
+
+    @sa @ref basic_json(const typename string_t::value_type*) -- create a
+    string value from a character pointer
+    @sa @ref basic_json(const CompatibleStringType&) -- create a string value
+    from a compatible string container
+
+    @since version 1.0.0
+    */
+    basic_json(const string_t& val)
+        : m_type(value_t::string), m_value(val)
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create a string (explicit)
+
+    Create a string JSON value with a given content.
+
+    @param[in] val  a literal value for the string
+
+    @complexity Linear in the size of the passed @a val.
+
+    @throw std::bad_alloc if allocation for string value fails
+
+    @liveexample{The following code shows the constructor with string literal
+    parameter.,basic_json__string_t_value_type}
+
+    @sa @ref basic_json(const string_t&) -- create a string value
+    @sa @ref basic_json(const CompatibleStringType&) -- create a string value
+    from a compatible string container
+
+    @since version 1.0.0
+    */
+    basic_json(const typename string_t::value_type* val)
+        : basic_json(string_t(val))
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create a string (implicit)
+
+    Create a string JSON value with a given content.
+
+    @param[in] val  a value for the string
+
+    @tparam CompatibleStringType an string type which is compatible to @ref
+    string_t, for instance `std::string`.
+
+    @complexity Linear in the size of the passed @a val.
+
+    @throw std::bad_alloc if allocation for string value fails
+
+    @liveexample{The following code shows the construction of a string value
+    from a compatible type.,basic_json__CompatibleStringType}
+
+    @sa @ref basic_json(const string_t&) -- create a string value
+    @sa @ref basic_json(const typename string_t::value_type*) -- create a
+    string value from a character pointer
+
+    @since version 1.0.0
+    */
+    template<class CompatibleStringType, typename std::enable_if<
+                 std::is_constructible<string_t, CompatibleStringType>::value, int>::type = 0>
+    basic_json(const CompatibleStringType& val)
+        : basic_json(string_t(val))
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create a boolean (explicit)
+
+    Creates a JSON boolean type from a given value.
+
+    @param[in] val  a boolean value to store
+
+    @complexity Constant.
+
+    @liveexample{The example below demonstrates boolean
+    values.,basic_json__boolean_t}
+
+    @since version 1.0.0
+    */
+    basic_json(boolean_t val) noexcept
+        : m_type(value_t::boolean), m_value(val)
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an integer number (explicit)
+
+    Create an integer number JSON value with a given content.
+
+    @tparam T A helper type to remove this function via SFINAE in case @ref
+    number_integer_t is the same as `int`. In this case, this constructor
+    would have the same signature as @ref basic_json(const int value). Note
+    the helper type @a T is not visible in this constructor's interface.
+
+    @param[in] val  an integer to create a JSON number from
+
+    @complexity Constant.
+
+    @liveexample{The example below shows the construction of an integer
+    number value.,basic_json__number_integer_t}
+
+    @sa @ref basic_json(const int) -- create a number value (integer)
+    @sa @ref basic_json(const CompatibleNumberIntegerType) -- create a number
+    value (integer) from a compatible number type
+
+    @since version 1.0.0
+    */
+    template<typename T, typename std::enable_if<
+                 not (std::is_same<T, int>::value) and
+                 std::is_same<T, number_integer_t>::value, int>::type = 0>
+    basic_json(const number_integer_t val) noexcept
+        : m_type(value_t::number_integer), m_value(val)
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an integer number from an enum type (explicit)
+
+    Create an integer number JSON value with a given content.
+
+    @param[in] val  an integer to create a JSON number from
+
+    @note This constructor allows to pass enums directly to a constructor. As
+    C++ has no way of specifying the type of an anonymous enum explicitly, we
+    can only rely on the fact that such values implicitly convert to int. As
+    int may already be the same type of number_integer_t, we may need to
+    switch off the constructor @ref basic_json(const number_integer_t).
+
+    @complexity Constant.
+
+    @liveexample{The example below shows the construction of an integer
+    number value from an anonymous enum.,basic_json__const_int}
+
+    @sa @ref basic_json(const number_integer_t) -- create a number value
+    (integer)
+    @sa @ref basic_json(const CompatibleNumberIntegerType) -- create a number
+    value (integer) from a compatible number type
+
+    @since version 1.0.0
+    */
+    basic_json(const int val) noexcept
+        : m_type(value_t::number_integer),
+          m_value(static_cast<number_integer_t>(val))
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an integer number (implicit)
+
+    Create an integer number JSON value with a given content. This constructor
+    allows any type @a CompatibleNumberIntegerType that can be used to
+    construct values of type @ref number_integer_t.
+
+    @tparam CompatibleNumberIntegerType An integer type which is compatible to
+    @ref number_integer_t. Examples include the types `int`, `int32_t`,
+    `long`, and `short`.
+
+    @param[in] val  an integer to create a JSON number from
+
+    @complexity Constant.
+
+    @liveexample{The example below shows the construction of several integer
+    number values from compatible
+    types.,basic_json__CompatibleIntegerNumberType}
+
+    @sa @ref basic_json(const number_integer_t) -- create a number value
+    (integer)
+    @sa @ref basic_json(const int) -- create a number value (integer)
+
+    @since version 1.0.0
+    */
+    template<typename CompatibleNumberIntegerType, typename std::enable_if<
+                 std::is_constructible<number_integer_t, CompatibleNumberIntegerType>::value and
+                 std::numeric_limits<CompatibleNumberIntegerType>::is_integer and
+                 std::numeric_limits<CompatibleNumberIntegerType>::is_signed,
+                 CompatibleNumberIntegerType>::type = 0>
+    basic_json(const CompatibleNumberIntegerType val) noexcept
+        : m_type(value_t::number_integer),
+          m_value(static_cast<number_integer_t>(val))
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an unsigned integer number (explicit)
+
+    Create an unsigned integer number JSON value with a given content.
+
+    @tparam T  helper type to compare number_unsigned_t and unsigned int (not
+    visible in) the interface.
+
+    @param[in] val  an integer to create a JSON number from
+
+    @complexity Constant.
+
+    @sa @ref basic_json(const CompatibleNumberUnsignedType) -- create a number
+    value (unsigned integer) from a compatible number type
+
+    @since version 2.0.0
+    */
+    template<typename T, typename std::enable_if<
+                 not (std::is_same<T, int>::value) and
+                 std::is_same<T, number_unsigned_t>::value, int>::type = 0>
+    basic_json(const number_unsigned_t val) noexcept
+        : m_type(value_t::number_unsigned), m_value(val)
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an unsigned number (implicit)
+
+    Create an unsigned number JSON value with a given content. This
+    constructor allows any type @a CompatibleNumberUnsignedType that can be
+    used to construct values of type @ref number_unsigned_t.
+
+    @tparam CompatibleNumberUnsignedType An integer type which is compatible
+    to @ref number_unsigned_t. Examples may include the types `unsigned int`,
+    `uint32_t`, or `unsigned short`.
+
+    @param[in] val  an unsigned integer to create a JSON number from
+
+    @complexity Constant.
+
+    @sa @ref basic_json(const number_unsigned_t) -- create a number value
+    (unsigned)
+
+    @since version 2.0.0
+    */
+    template<typename CompatibleNumberUnsignedType, typename std::enable_if <
+                 std::is_constructible<number_unsigned_t, CompatibleNumberUnsignedType>::value and
+                 std::numeric_limits<CompatibleNumberUnsignedType>::is_integer and
+                 not std::numeric_limits<CompatibleNumberUnsignedType>::is_signed,
+                 CompatibleNumberUnsignedType>::type = 0>
+    basic_json(const CompatibleNumberUnsignedType val) noexcept
+        : m_type(value_t::number_unsigned),
+          m_value(static_cast<number_unsigned_t>(val))
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create a floating-point number (explicit)
+
+    Create a floating-point number JSON value with a given content.
+
+    @param[in] val  a floating-point value to create a JSON number from
+
+    @note [RFC 7159](http://www.rfc-editor.org/rfc/rfc7159.txt), section 6
+    disallows NaN values:
+    > Numeric values that cannot be represented in the grammar below (such as
+    > Infinity and NaN) are not permitted.
+    In case the parameter @a val is not a number, a JSON null value is created
+    instead.
+
+    @complexity Constant.
+
+    @liveexample{The following example creates several floating-point
+    values.,basic_json__number_float_t}
+
+    @sa @ref basic_json(const CompatibleNumberFloatType) -- create a number
+    value (floating-point) from a compatible number type
+
+    @since version 1.0.0
+    */
+    basic_json(const number_float_t val) noexcept
+        : m_type(value_t::number_float), m_value(val)
+    {
+        // replace infinity and NAN by null
+        if (not std::isfinite(val))
+        {
+            m_type = value_t::null;
+            m_value = json_value();
+        }
+
+        assert_invariant();
+    }
+
+    /*!
+    @brief create an floating-point number (implicit)
+
+    Create an floating-point number JSON value with a given content. This
+    constructor allows any type @a CompatibleNumberFloatType that can be used
+    to construct values of type @ref number_float_t.
+
+    @tparam CompatibleNumberFloatType A floating-point type which is
+    compatible to @ref number_float_t. Examples may include the types `float`
+    or `double`.
+
+    @param[in] val  a floating-point to create a JSON number from
+
+    @note [RFC 7159](http://www.rfc-editor.org/rfc/rfc7159.txt), section 6
+    disallows NaN values:
+    > Numeric values that cannot be represented in the grammar below (such as
+    > Infinity and NaN) are not permitted.
+    In case the parameter @a val is not a number, a JSON null value is
+    created instead.
+
+    @complexity Constant.
+
+    @liveexample{The example below shows the construction of several
+    floating-point number values from compatible
+    types.,basic_json__CompatibleNumberFloatType}
+
+    @sa @ref basic_json(const number_float_t) -- create a number value
+    (floating-point)
+
+    @since version 1.0.0
+    */
+    template<typename CompatibleNumberFloatType, typename = typename std::enable_if<
+                 std::is_constructible<number_float_t, CompatibleNumberFloatType>::value and
+                 std::is_floating_point<CompatibleNumberFloatType>::value>::type>
+    basic_json(const CompatibleNumberFloatType val) noexcept
+        : basic_json(number_float_t(val))
+    {
+        assert_invariant();
+    }
+
+    /*!
+    @brief create a container (array or object) from an initializer list
+
+    Creates a JSON value of type array or object from the passed initializer
+    list @a init. In case @a type_deduction is `true` (default), the type of
+    the JSON value to be created is deducted from the initializer list @a init
+    according to the following rules:
+
+    1. If the list is empty, an empty JSON object value `{}` is created.
+    2. If the list consists of pairs whose first element is a string, a JSON
+       object value is created where the first elements of the pairs are
+       treated as keys and the second elements are as values.
+    3. In all other cases, an array is created.
+
+    The rules aim to create the best fit between a C++ initializer list and
+    JSON values. The rationale is as follows:
+
+    1. The empty initializer list is written as `{}` which is exactly an empty
+       JSON object.
+    2. C++ has now way of describing mapped types other than to list a list of
+       pairs. As JSON requires that keys must be of type string, rule 2 is the
+       weakest constraint one can pose on initializer lists to interpret them
+       as an object.
+    3. In all other cases, the initializer list could not be interpreted as
+       JSON object type, so interpreting it as JSON array type is safe.
+
+    With the rules described above, the following JSON values cannot be
+    expressed by an initializer list:
+
+    - the empty array (`[]`): use @ref array(std::initializer_list<basic_json>)
+      with an empty initializer list in this case
+    - arrays whose elements satisfy rule 2: use @ref
+      array(std::initializer_list<basic_json>) with the same initializer list
+      in this case
+
+    @note When used without parentheses around an empty initializer list, @ref
+    basic_json() is called instead of this function, yielding the JSON null
+    value.
+
+    @param[in] init  initializer list with JSON values
+
+    @param[in] type_deduction internal parameter; when set to `true`, the type
+    of the JSON value is deducted from the initializer list @a init; when set
+    to `false`, the type provided via @a manual_type is forced. This mode is
+    used by the functions @ref array(std::initializer_list<basic_json>) and
+    @ref object(std::initializer_list<basic_json>).
+
+    @param[in] manual_type internal parameter; when @a type_deduction is set
+    to `false`, the created JSON value will use the provided type (only @ref
+    value_t::array and @ref value_t::object are valid); when @a type_deduction
+    is set to `true`, this parameter has no effect
+
+    @throw std::domain_error if @a type_deduction is `false`, @a manual_type
+    is `value_t::object`, but @a init contains an element which is not a pair
+    whose first element is a string; example: `"cannot create object from
+    initializer list"`
+
+    @complexity Linear in the size of the initializer list @a init.
+
+    @liveexample{The example below shows how JSON values are created from
+    initializer lists.,basic_json__list_init_t}
+
+    @sa @ref array(std::initializer_list<basic_json>) -- create a JSON array
+    value from an initializer list
+    @sa @ref object(std::initializer_list<basic_json>) -- create a JSON object
+    value from an initializer list
+
+    @since version 1.0.0
+    */
+    basic_json(std::initializer_list<basic_json> init,
+               bool type_deduction = true,
+               value_t manual_type = value_t::array)
+    {
+        // check if each element is an array with two elements whose first
+        // element is a string
+        bool is_an_object = std::all_of(init.begin(), init.end(),
+                                        [](const basic_json & element)
+        {
+            return element.is_array() and element.size() == 2 and element[0].is_string();
+        });
+
+        // adjust type if type deduction is not wanted
+        if (not type_deduction)
+        {
+            // if array is wanted, do not create an object though possible
+            if (manual_type == value_t::array)
+            {
+                is_an_object = false;
+            }
+
+            // if object is wanted but impossible, throw an exception
+            if (manual_type == value_t::object and not is_an_object)
+            {
+                throw std::domain_error("cannot create object from initializer list");
+            }
+        }
+
+        if (is_an_object)
+        {
+            // the initializer list is a list of pairs -> create object
+            m_type = value_t::object;
+            m_value = value_t::object;
+
+            std::for_each(init.begin(), init.end(), [this](const basic_json & element)
+            {
+                m_value.object->emplace(*(element[0].m_value.string), element[1]);
+            });
+        }
+        else
+        {
+            // the initializer list describes an array -> create array
+            m_type = value_t::array;
+            m_value.array = create<array_t>(init);
+        }
+
+        assert_invariant();
+    }
+
+    /*!
+    @brief explicitly create an array from an initializer list
+
+    Creates a JSON array value from a given initializer list. That is, given a
+    list of values `a, b, c`, creates the JSON value `[a, b, c]`. If the
+    initializer list is empty, the empty array `[]` is created.
+
+    @note This function is only needed to express two edge cases that cannot
+    be realized with the initializer list constructor (@ref
+    basic_json(std::initializer_list<basic_json>, bool, value_t)). These cases
+    are:
+    1. creating an array whose elements are all pairs whose first element is a
+    string -- in this case, the initializer list constructor would create an
+    object, taking the first elements as keys
+    2. creating an empty array -- passing the empty initializer list to the
+    initializer list constructor yields an empty object
+
+    @param[in] init  initializer list with JSON values to create an array from
+    (optional)
+
+    @return JSON array value
+
+    @complexity Linear in the size of @a init.
+
+    @liveexample{The following code shows an example for the `array`
+    function.,array}
+
+    @sa @ref basic_json(std::initializer_list<basic_json>, bool, value_t) --
+    create a JSON value from an initializer list
+    @sa @ref object(std::initializer_list<basic_json>) -- create a JSON object
+    value from an initializer list
+
+    @since version 1.0.0
+    */
+    static basic_json array(std::initializer_list<basic_json> init =
+                                std::initializer_list<basic_json>())
+    {
+        return basic_json(init, false, value_t::array);
+    }
+
+    /*!
+    @brief explicitly create an object from an initializer list
+
+    Creates a JSON object value from a given initializer list. The initializer
+    lists elements must be pairs, and their first elements must be strings. If
+    the initializer list is empty, the empty object `{}` is created.
+
+    @note This function is only added for symmetry reasons. In contrast to the
+    related function @ref array(std::initializer_list<basic_json>), there are
+    no cases which can only be expressed by this function. That is, any
+    initializer list @a init can also be passed to the initializer list
+    constructor @ref basic_json(std::initializer_list<basic_json>, bool,
+    value_t).
+
+    @param[in] init  initializer list to create an object from (optional)
+
+    @return JSON object value
+
+    @throw std::domain_error if @a init is not a pair whose first elements are
+    strings; thrown by
+    @ref basic_json(std::initializer_list<basic_json>, bool, value_t)
+
+    @complexity Linear in the size of @a init.
+
+    @liveexample{The following code shows an example for the `object`
+    function.,object}
+
+    @sa @ref basic_json(std::initializer_list<basic_json>, bool, value_t) --
+    create a JSON value from an initializer list
+    @sa @ref array(std::initializer_list<basic_json>) -- create a JSON array
+    value from an initializer list
+
+    @since version 1.0.0
+    */
+    static basic_json object(std::initializer_list<basic_json> init =
+                                 std::initializer_list<basic_json>())
+    {
+        return basic_json(init, false, value_t::object);
+    }
+
+    /*!
+    @brief construct an array with count copies of given value
+
+    Constructs a JSON array value by creating @a cnt copies of a passed value.
+    In case @a cnt is `0`, an empty array is created. As postcondition,
+    `std::distance(begin(),end()) == cnt` holds.
+
+    @param[in] cnt  the number of JSON copies of @a val to create
+    @param[in] val  the JSON value to copy
+
+    @complexity Linear in @a cnt.
+
+    @liveexample{The following code shows examples for the @ref
+    basic_json(size_type\, const basic_json&)
+    constructor.,basic_json__size_type_basic_json}
+
+    @since version 1.0.0
+    */
+    basic_json(size_type cnt, const basic_json& val)
+        : m_type(value_t::array)
+    {
+        m_value.array = create<array_t>(cnt, val);
+        assert_invariant();
+    }
+
+    /*!
+    @brief construct a JSON container given an iterator range
+
+    Constructs the JSON value with the contents of the range `[first, last)`.
+    The semantics depends on the different types a JSON value can have:
+    - In case of primitive types (number, boolean, or string), @a first must
+      be `begin()` and @a last must be `end()`. In this case, the value is
+      copied. Otherwise, std::out_of_range is thrown.
+    - In case of structured types (array, object), the constructor behaves as
+      similar versions for `std::vector`.
+    - In case of a null type, std::domain_error is thrown.
+
+    @tparam InputIT an input iterator type (@ref iterator or @ref
+    const_iterator)
+
+    @param[in] first begin of the range to copy from (included)
+    @param[in] last end of the range to copy from (excluded)
+
+    @pre Iterators @a first and @a last must be initialized. **This
+         precondition is enforced with an assertion.**
+
+    @throw std::domain_error if iterators are not compatible; that is, do not
+    belong to the same JSON value; example: `"iterators are not compatible"`
+    @throw std::out_of_range if iterators are for a primitive type (number,
+    boolean, or string) where an out of range error can be detected easily;
+    example: `"iterators out of range"`
+    @throw std::bad_alloc if allocation for object, array, or string fails
+    @throw std::domain_error if called with a null value; example: `"cannot
+    use construct with iterators from null"`
+
+    @complexity Linear in distance between @a first and @a last.
+
+    @liveexample{The example below shows several ways to create JSON values by
+    specifying a subrange with iterators.,basic_json__InputIt_InputIt}
+
+    @since version 1.0.0
+    */
+    template<class InputIT, typename std::enable_if<
+                 std::is_same<InputIT, typename basic_json_t::iterator>::value or
+                 std::is_same<InputIT, typename basic_json_t::const_iterator>::value, int>::type = 0>
+    basic_json(InputIT first, InputIT last)
+    {
+        assert(first.m_object != nullptr);
+        assert(last.m_object != nullptr);
+
+        // make sure iterator fits the current value
+        if (first.m_object != last.m_object)
+        {
+            throw std::domain_error("iterators are not compatible");
+        }
+
+        // copy type from first iterator
+        m_type = first.m_object->m_type;
+
+        // check if iterator range is complete for primitive values
+        switch (m_type)
+        {
+            case value_t::boolean:
+            case value_t::number_float:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::string:
+            {
+                if (not first.m_it.primitive_iterator.is_begin() or not last.m_it.primitive_iterator.is_end())
+                {
+                    throw std::out_of_range("iterators out of range");
+                }
+                break;
+            }
+
+            default:
+            {
+                break;
+            }
+        }
+
+        switch (m_type)
+        {
+            case value_t::number_integer:
+            {
+                m_value.number_integer = first.m_object->m_value.number_integer;
+                break;
+            }
+
+            case value_t::number_unsigned:
+            {
+                m_value.number_unsigned = first.m_object->m_value.number_unsigned;
+                break;
+            }
+
+            case value_t::number_float:
+            {
+                m_value.number_float = first.m_object->m_value.number_float;
+                break;
+            }
+
+            case value_t::boolean:
+            {
+                m_value.boolean = first.m_object->m_value.boolean;
+                break;
+            }
+
+            case value_t::string:
+            {
+                m_value = *first.m_object->m_value.string;
+                break;
+            }
+
+            case value_t::object:
+            {
+                m_value.object = create<object_t>(first.m_it.object_iterator, last.m_it.object_iterator);
+                break;
+            }
+
+            case value_t::array:
+            {
+                m_value.array = create<array_t>(first.m_it.array_iterator, last.m_it.array_iterator);
+                break;
+            }
+
+            default:
+            {
+                throw std::domain_error("cannot use construct with iterators from " + first.m_object->type_name());
+            }
+        }
+
+        assert_invariant();
+    }
+
+    /*!
+    @brief construct a JSON value given an input stream
+
+    @param[in,out] i  stream to read a serialized JSON value from
+    @param[in] cb a parser callback function of type @ref parser_callback_t
+    which is used to control the deserialization by filtering unwanted values
+    (optional)
+
+    @complexity Linear in the length of the input. The parser is a predictive
+    LL(1) parser. The complexity can be higher if the parser callback function
+    @a cb has a super-linear complexity.
+
+    @note A UTF-8 byte order mark is silently ignored.
+
+    @deprecated This constructor is deprecated and will be removed in version
+      3.0.0 to unify the interface of the library. Deserialization will be
+      done by stream operators or by calling one of the `parse` functions,
+      e.g. @ref parse(std::istream&, const parser_callback_t). That is, calls
+      like `json j(i);` for an input stream @a i need to be replaced by
+      `json j = json::parse(i);`. See the example below.
+
+    @liveexample{The example below demonstrates constructing a JSON value from
+    a `std::stringstream` with and without callback
+    function.,basic_json__istream}
+
+    @since version 2.0.0, deprecated in version 2.0.3, to be removed in
+           version 3.0.0
+    */
+    JSON_DEPRECATED
+    explicit basic_json(std::istream& i, const parser_callback_t cb = nullptr)
+    {
+        *this = parser(i, cb).parse();
+        assert_invariant();
+    }
+
+    ///////////////////////////////////////
+    // other constructors and destructor //
+    ///////////////////////////////////////
+
+    /*!
+    @brief copy constructor
+
+    Creates a copy of a given JSON value.
+
+    @param[in] other  the JSON value to copy
+
+    @complexity Linear in the size of @a other.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is linear.
+    - As postcondition, it holds: `other == basic_json(other)`.
+
+    @throw std::bad_alloc if allocation for object, array, or string fails.
+
+    @liveexample{The following code shows an example for the copy
+    constructor.,basic_json__basic_json}
+
+    @since version 1.0.0
+    */
+    basic_json(const basic_json& other)
+        : m_type(other.m_type)
+    {
+        // check of passed value is valid
+        other.assert_invariant();
+
+        switch (m_type)
+        {
+            case value_t::object:
+            {
+                m_value = *other.m_value.object;
+                break;
+            }
+
+            case value_t::array:
+            {
+                m_value = *other.m_value.array;
+                break;
+            }
+
+            case value_t::string:
+            {
+                m_value = *other.m_value.string;
+                break;
+            }
+
+            case value_t::boolean:
+            {
+                m_value = other.m_value.boolean;
+                break;
+            }
+
+            case value_t::number_integer:
+            {
+                m_value = other.m_value.number_integer;
+                break;
+            }
+
+            case value_t::number_unsigned:
+            {
+                m_value = other.m_value.number_unsigned;
+                break;
+            }
+
+            case value_t::number_float:
+            {
+                m_value = other.m_value.number_float;
+                break;
+            }
+
+            default:
+            {
+                break;
+            }
+        }
+
+        assert_invariant();
+    }
+
+    /*!
+    @brief move constructor
+
+    Move constructor. Constructs a JSON value with the contents of the given
+    value @a other using move semantics. It "steals" the resources from @a
+    other and leaves it as JSON null value.
+
+    @param[in,out] other  value to move to this object
+
+    @post @a other is a JSON null value
+
+    @complexity Constant.
+
+    @liveexample{The code below shows the move constructor explicitly called
+    via std::move.,basic_json__moveconstructor}
+
+    @since version 1.0.0
+    */
+    basic_json(basic_json&& other) noexcept
+        : m_type(std::move(other.m_type)),
+          m_value(std::move(other.m_value))
+    {
+        // check that passed value is valid
+        other.assert_invariant();
+
+        // invalidate payload
+        other.m_type = value_t::null;
+        other.m_value = {};
+
+        assert_invariant();
+    }
+
+    /*!
+    @brief copy assignment
+
+    Copy assignment operator. Copies a JSON value via the "copy and swap"
+    strategy: It is expressed in terms of the copy constructor, destructor,
+    and the swap() member function.
+
+    @param[in] other  value to copy from
+
+    @complexity Linear.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is linear.
+
+    @liveexample{The code below shows and example for the copy assignment. It
+    creates a copy of value `a` which is then swapped with `b`. Finally\, the
+    copy of `a` (which is the null value after the swap) is
+    destroyed.,basic_json__copyassignment}
+
+    @since version 1.0.0
+    */
+    reference& operator=(basic_json other) noexcept (
+        std::is_nothrow_move_constructible<value_t>::value and
+        std::is_nothrow_move_assignable<value_t>::value and
+        std::is_nothrow_move_constructible<json_value>::value and
+        std::is_nothrow_move_assignable<json_value>::value
+    )
+    {
+        // check that passed value is valid
+        other.assert_invariant();
+
+        using std::swap;
+        swap(m_type, other.m_type);
+        swap(m_value, other.m_value);
+
+        assert_invariant();
+        return *this;
+    }
+
+    /*!
+    @brief destructor
+
+    Destroys the JSON value and frees all allocated memory.
+
+    @complexity Linear.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is linear.
+    - All stored elements are destroyed and all memory is freed.
+
+    @since version 1.0.0
+    */
+    ~basic_json()
+    {
+        assert_invariant();
+
+        switch (m_type)
+        {
+            case value_t::object:
+            {
+                AllocatorType<object_t> alloc;
+                alloc.destroy(m_value.object);
+                alloc.deallocate(m_value.object, 1);
+                break;
+            }
+
+            case value_t::array:
+            {
+                AllocatorType<array_t> alloc;
+                alloc.destroy(m_value.array);
+                alloc.deallocate(m_value.array, 1);
+                break;
+            }
+
+            case value_t::string:
+            {
+                AllocatorType<string_t> alloc;
+                alloc.destroy(m_value.string);
+                alloc.deallocate(m_value.string, 1);
+                break;
+            }
+
+            default:
+            {
+                // all other types need no specific destructor
+                break;
+            }
+        }
+    }
+
+    /// @}
+
+  public:
+    ///////////////////////
+    // object inspection //
+    ///////////////////////
+
+    /// @name object inspection
+    /// Functions to inspect the type of a JSON value.
+    /// @{
+
+    /*!
+    @brief serialization
+
+    Serialization function for JSON values. The function tries to mimic
+    Python's `json.dumps()` function, and currently supports its @a indent
+    parameter.
+
+    @param[in] indent If indent is nonnegative, then array elements and object
+    members will be pretty-printed with that indent level. An indent level of
+    `0` will only insert newlines. `-1` (the default) selects the most compact
+    representation.
+
+    @return string containing the serialization of the JSON value
+
+    @complexity Linear.
+
+    @liveexample{The following example shows the effect of different @a indent
+    parameters to the result of the serialization.,dump}
+
+    @see https://docs.python.org/2/library/json.html#json.dump
+
+    @since version 1.0.0
+    */
+    string_t dump(const int indent = -1) const
+    {
+        std::stringstream ss;
+        // fix locale problems
+        const static std::locale loc(std::locale(), new DecimalSeparator);
+        ss.imbue(loc);
+
+        // 6, 15 or 16 digits of precision allows round-trip IEEE 754
+        // string->float->string, string->double->string or string->long
+        // double->string; to be safe, we read this value from
+        // std::numeric_limits<number_float_t>::digits10
+        ss.precision(std::numeric_limits<double>::digits10);
+
+        if (indent >= 0)
+        {
+            dump(ss, true, static_cast<unsigned int>(indent));
+        }
+        else
+        {
+            dump(ss, false, 0);
+        }
+
+        return ss.str();
+    }
+
+    /*!
+    @brief return the type of the JSON value (explicit)
+
+    Return the type of the JSON value as a value from the @ref value_t
+    enumeration.
+
+    @return the type of the JSON value
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `type()` for all JSON
+    types.,type}
+
+    @since version 1.0.0
+    */
+    constexpr value_t type() const noexcept
+    {
+        return m_type;
+    }
+
+    /*!
+    @brief return whether type is primitive
+
+    This function returns true iff the JSON type is primitive (string, number,
+    boolean, or null).
+
+    @return `true` if type is primitive (string, number, boolean, or null),
+    `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_primitive()` for all JSON
+    types.,is_primitive}
+
+    @sa @ref is_structured() -- returns whether JSON value is structured
+    @sa @ref is_null() -- returns whether JSON value is `null`
+    @sa @ref is_string() -- returns whether JSON value is a string
+    @sa @ref is_boolean() -- returns whether JSON value is a boolean
+    @sa @ref is_number() -- returns whether JSON value is a number
+
+    @since version 1.0.0
+    */
+    constexpr bool is_primitive() const noexcept
+    {
+        return is_null() or is_string() or is_boolean() or is_number();
+    }
+
+    /*!
+    @brief return whether type is structured
+
+    This function returns true iff the JSON type is structured (array or
+    object).
+
+    @return `true` if type is structured (array or object), `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_structured()` for all JSON
+    types.,is_structured}
+
+    @sa @ref is_primitive() -- returns whether value is primitive
+    @sa @ref is_array() -- returns whether value is an array
+    @sa @ref is_object() -- returns whether value is an object
+
+    @since version 1.0.0
+    */
+    constexpr bool is_structured() const noexcept
+    {
+        return is_array() or is_object();
+    }
+
+    /*!
+    @brief return whether value is null
+
+    This function returns true iff the JSON value is null.
+
+    @return `true` if type is null, `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_null()` for all JSON
+    types.,is_null}
+
+    @since version 1.0.0
+    */
+    constexpr bool is_null() const noexcept
+    {
+        return m_type == value_t::null;
+    }
+
+    /*!
+    @brief return whether value is a boolean
+
+    This function returns true iff the JSON value is a boolean.
+
+    @return `true` if type is boolean, `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_boolean()` for all JSON
+    types.,is_boolean}
+
+    @since version 1.0.0
+    */
+    constexpr bool is_boolean() const noexcept
+    {
+        return m_type == value_t::boolean;
+    }
+
+    /*!
+    @brief return whether value is a number
+
+    This function returns true iff the JSON value is a number. This includes
+    both integer and floating-point values.
+
+    @return `true` if type is number (regardless whether integer, unsigned
+    integer or floating-type), `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_number()` for all JSON
+    types.,is_number}
+
+    @sa @ref is_number_integer() -- check if value is an integer or unsigned
+    integer number
+    @sa @ref is_number_unsigned() -- check if value is an unsigned integer
+    number
+    @sa @ref is_number_float() -- check if value is a floating-point number
+
+    @since version 1.0.0
+    */
+    constexpr bool is_number() const noexcept
+    {
+        return is_number_integer() or is_number_float();
+    }
+
+    /*!
+    @brief return whether value is an integer number
+
+    This function returns true iff the JSON value is an integer or unsigned
+    integer number. This excludes floating-point values.
+
+    @return `true` if type is an integer or unsigned integer number, `false`
+    otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_number_integer()` for all
+    JSON types.,is_number_integer}
+
+    @sa @ref is_number() -- check if value is a number
+    @sa @ref is_number_unsigned() -- check if value is an unsigned integer
+    number
+    @sa @ref is_number_float() -- check if value is a floating-point number
+
+    @since version 1.0.0
+    */
+    constexpr bool is_number_integer() const noexcept
+    {
+        return m_type == value_t::number_integer or m_type == value_t::number_unsigned;
+    }
+
+    /*!
+    @brief return whether value is an unsigned integer number
+
+    This function returns true iff the JSON value is an unsigned integer
+    number. This excludes floating-point and (signed) integer values.
+
+    @return `true` if type is an unsigned integer number, `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_number_unsigned()` for all
+    JSON types.,is_number_unsigned}
+
+    @sa @ref is_number() -- check if value is a number
+    @sa @ref is_number_integer() -- check if value is an integer or unsigned
+    integer number
+    @sa @ref is_number_float() -- check if value is a floating-point number
+
+    @since version 2.0.0
+    */
+    constexpr bool is_number_unsigned() const noexcept
+    {
+        return m_type == value_t::number_unsigned;
+    }
+
+    /*!
+    @brief return whether value is a floating-point number
+
+    This function returns true iff the JSON value is a floating-point number.
+    This excludes integer and unsigned integer values.
+
+    @return `true` if type is a floating-point number, `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_number_float()` for all
+    JSON types.,is_number_float}
+
+    @sa @ref is_number() -- check if value is number
+    @sa @ref is_number_integer() -- check if value is an integer number
+    @sa @ref is_number_unsigned() -- check if value is an unsigned integer
+    number
+
+    @since version 1.0.0
+    */
+    constexpr bool is_number_float() const noexcept
+    {
+        return m_type == value_t::number_float;
+    }
+
+    /*!
+    @brief return whether value is an object
+
+    This function returns true iff the JSON value is an object.
+
+    @return `true` if type is object, `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_object()` for all JSON
+    types.,is_object}
+
+    @since version 1.0.0
+    */
+    constexpr bool is_object() const noexcept
+    {
+        return m_type == value_t::object;
+    }
+
+    /*!
+    @brief return whether value is an array
+
+    This function returns true iff the JSON value is an array.
+
+    @return `true` if type is array, `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_array()` for all JSON
+    types.,is_array}
+
+    @since version 1.0.0
+    */
+    constexpr bool is_array() const noexcept
+    {
+        return m_type == value_t::array;
+    }
+
+    /*!
+    @brief return whether value is a string
+
+    This function returns true iff the JSON value is a string.
+
+    @return `true` if type is string, `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_string()` for all JSON
+    types.,is_string}
+
+    @since version 1.0.0
+    */
+    constexpr bool is_string() const noexcept
+    {
+        return m_type == value_t::string;
+    }
+
+    /*!
+    @brief return whether value is discarded
+
+    This function returns true iff the JSON value was discarded during parsing
+    with a callback function (see @ref parser_callback_t).
+
+    @note This function will always be `false` for JSON values after parsing.
+    That is, discarded values can only occur during parsing, but will be
+    removed when inside a structured value or replaced by null in other cases.
+
+    @return `true` if type is discarded, `false` otherwise.
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies `is_discarded()` for all JSON
+    types.,is_discarded}
+
+    @since version 1.0.0
+    */
+    constexpr bool is_discarded() const noexcept
+    {
+        return m_type == value_t::discarded;
+    }
+
+    /*!
+    @brief return the type of the JSON value (implicit)
+
+    Implicitly return the type of the JSON value as a value from the @ref
+    value_t enumeration.
+
+    @return the type of the JSON value
+
+    @complexity Constant.
+
+    @exceptionsafety No-throw guarantee: this member function never throws
+    exceptions.
+
+    @liveexample{The following code exemplifies the @ref value_t operator for
+    all JSON types.,operator__value_t}
+
+    @since version 1.0.0
+    */
+    constexpr operator value_t() const noexcept
+    {
+        return m_type;
+    }
+
+    /// @}
+
+  private:
+    //////////////////
+    // value access //
+    //////////////////
+
+    /// get an object (explicit)
+    template<class T, typename std::enable_if<
+                 std::is_convertible<typename object_t::key_type, typename T::key_type>::value and
+                 std::is_convertible<basic_json_t, typename T::mapped_type>::value, int>::type = 0>
+    T get_impl(T*) const
+    {
+        if (is_object())
+        {
+            return T(m_value.object->begin(), m_value.object->end());
+        }
+        else
+        {
+            throw std::domain_error("type must be object, but is " + type_name());
+        }
+    }
+
+    /// get an object (explicit)
+    object_t get_impl(object_t*) const
+    {
+        if (is_object())
+        {
+            return *(m_value.object);
+        }
+        else
+        {
+            throw std::domain_error("type must be object, but is " + type_name());
+        }
+    }
+
+    /// get an array (explicit)
+    template<class T, typename std::enable_if<
+                 std::is_convertible<basic_json_t, typename T::value_type>::value and
+                 not std::is_same<basic_json_t, typename T::value_type>::value and
+                 not std::is_arithmetic<T>::value and
+                 not std::is_convertible<std::string, T>::value and
+                 not has_mapped_type<T>::value, int>::type = 0>
+    T get_impl(T*) const
+    {
+        if (is_array())
+        {
+            T to_vector;
+            std::transform(m_value.array->begin(), m_value.array->end(),
+                           std::inserter(to_vector, to_vector.end()), [](basic_json i)
+            {
+                return i.get<typename T::value_type>();
+            });
+            return to_vector;
+        }
+        else
+        {
+            throw std::domain_error("type must be array, but is " + type_name());
+        }
+    }
+
+    /// get an array (explicit)
+    template<class T, typename std::enable_if<
+                 std::is_convertible<basic_json_t, T>::value and
+                 not std::is_same<basic_json_t, T>::value, int>::type = 0>
+    std::vector<T> get_impl(std::vector<T>*) const
+    {
+        if (is_array())
+        {
+            std::vector<T> to_vector;
+            to_vector.reserve(m_value.array->size());
+            std::transform(m_value.array->begin(), m_value.array->end(),
+                           std::inserter(to_vector, to_vector.end()), [](basic_json i)
+            {
+                return i.get<T>();
+            });
+            return to_vector;
+        }
+        else
+        {
+            throw std::domain_error("type must be array, but is " + type_name());
+        }
+    }
+
+    /// get an array (explicit)
+    template<class T, typename std::enable_if<
+                 std::is_same<basic_json, typename T::value_type>::value and
+                 not has_mapped_type<T>::value, int>::type = 0>
+    T get_impl(T*) const
+    {
+        if (is_array())
+        {
+            return T(m_value.array->begin(), m_value.array->end());
+        }
+        else
+        {
+            throw std::domain_error("type must be array, but is " + type_name());
+        }
+    }
+
+    /// get an array (explicit)
+    array_t get_impl(array_t*) const
+    {
+        if (is_array())
+        {
+            return *(m_value.array);
+        }
+        else
+        {
+            throw std::domain_error("type must be array, but is " + type_name());
+        }
+    }
+
+    /// get a string (explicit)
+    template<typename T, typename std::enable_if<
+                 std::is_convertible<string_t, T>::value, int>::type = 0>
+    T get_impl(T*) const
+    {
+        if (is_string())
+        {
+            return *m_value.string;
+        }
+        else
+        {
+            throw std::domain_error("type must be string, but is " + type_name());
+        }
+    }
+
+    /// get a number (explicit)
+    template<typename T, typename std::enable_if<
+                 std::is_arithmetic<T>::value, int>::type = 0>
+    T get_impl(T*) const
+    {
+        switch (m_type)
+        {
+            case value_t::number_integer:
+            {
+                return static_cast<T>(m_value.number_integer);
+            }
+
+            case value_t::number_unsigned:
+            {
+                return static_cast<T>(m_value.number_unsigned);
+            }
+
+            case value_t::number_float:
+            {
+                return static_cast<T>(m_value.number_float);
+            }
+
+            default:
+            {
+                throw std::domain_error("type must be number, but is " + type_name());
+            }
+        }
+    }
+
+    /// get a boolean (explicit)
+    constexpr boolean_t get_impl(boolean_t*) const
+    {
+        return is_boolean()
+               ? m_value.boolean
+               : throw std::domain_error("type must be boolean, but is " + type_name());
+    }
+
+    /// get a pointer to the value (object)
+    object_t* get_impl_ptr(object_t*) noexcept
+    {
+        return is_object() ? m_value.object : nullptr;
+    }
+
+    /// get a pointer to the value (object)
+    constexpr const object_t* get_impl_ptr(const object_t*) const noexcept
+    {
+        return is_object() ? m_value.object : nullptr;
+    }
+
+    /// get a pointer to the value (array)
+    array_t* get_impl_ptr(array_t*) noexcept
+    {
+        return is_array() ? m_value.array : nullptr;
+    }
+
+    /// get a pointer to the value (array)
+    constexpr const array_t* get_impl_ptr(const array_t*) const noexcept
+    {
+        return is_array() ? m_value.array : nullptr;
+    }
+
+    /// get a pointer to the value (string)
+    string_t* get_impl_ptr(string_t*) noexcept
+    {
+        return is_string() ? m_value.string : nullptr;
+    }
+
+    /// get a pointer to the value (string)
+    constexpr const string_t* get_impl_ptr(const string_t*) const noexcept
+    {
+        return is_string() ? m_value.string : nullptr;
+    }
+
+    /// get a pointer to the value (boolean)
+    boolean_t* get_impl_ptr(boolean_t*) noexcept
+    {
+        return is_boolean() ? &m_value.boolean : nullptr;
+    }
+
+    /// get a pointer to the value (boolean)
+    constexpr const boolean_t* get_impl_ptr(const boolean_t*) const noexcept
+    {
+        return is_boolean() ? &m_value.boolean : nullptr;
+    }
+
+    /// get a pointer to the value (integer number)
+    number_integer_t* get_impl_ptr(number_integer_t*) noexcept
+    {
+        return is_number_integer() ? &m_value.number_integer : nullptr;
+    }
+
+    /// get a pointer to the value (integer number)
+    constexpr const number_integer_t* get_impl_ptr(const number_integer_t*) const noexcept
+    {
+        return is_number_integer() ? &m_value.number_integer : nullptr;
+    }
+
+    /// get a pointer to the value (unsigned number)
+    number_unsigned_t* get_impl_ptr(number_unsigned_t*) noexcept
+    {
+        return is_number_unsigned() ? &m_value.number_unsigned : nullptr;
+    }
+
+    /// get a pointer to the value (unsigned number)
+    constexpr const number_unsigned_t* get_impl_ptr(const number_unsigned_t*) const noexcept
+    {
+        return is_number_unsigned() ? &m_value.number_unsigned : nullptr;
+    }
+
+    /// get a pointer to the value (floating-point number)
+    number_float_t* get_impl_ptr(number_float_t*) noexcept
+    {
+        return is_number_float() ? &m_value.number_float : nullptr;
+    }
+
+    /// get a pointer to the value (floating-point number)
+    constexpr const number_float_t* get_impl_ptr(const number_float_t*) const noexcept
+    {
+        return is_number_float() ? &m_value.number_float : nullptr;
+    }
+
+    /*!
+    @brief helper function to implement get_ref()
+
+    This funcion helps to implement get_ref() without code duplication for
+    const and non-const overloads
+
+    @tparam ThisType will be deduced as `basic_json` or `const basic_json`
+
+    @throw std::domain_error if ReferenceType does not match underlying value
+    type of the current JSON
+    */
+    template<typename ReferenceType, typename ThisType>
+    static ReferenceType get_ref_impl(ThisType& obj)
+    {
+        // helper type
+        using PointerType = typename std::add_pointer<ReferenceType>::type;
+
+        // delegate the call to get_ptr<>()
+        auto ptr = obj.template get_ptr<PointerType>();
+
+        if (ptr != nullptr)
+        {
+            return *ptr;
+        }
+        else
+        {
+            throw std::domain_error("incompatible ReferenceType for get_ref, actual type is " +
+                                    obj.type_name());
+        }
+    }
+
+  public:
+
+    /// @name value access
+    /// Direct access to the stored value of a JSON value.
+    /// @{
+
+    /*!
+    @brief get a value (explicit)
+
+    Explicit type conversion between the JSON value and a compatible value.
+
+    @tparam ValueType non-pointer type compatible to the JSON value, for
+    instance `int` for JSON integer numbers, `bool` for JSON booleans, or
+    `std::vector` types for JSON arrays
+
+    @return copy of the JSON value, converted to type @a ValueType
+
+    @throw std::domain_error in case passed type @a ValueType is incompatible
+    to JSON; example: `"type must be object, but is null"`
+
+    @complexity Linear in the size of the JSON value.
+
+    @liveexample{The example below shows several conversions from JSON values
+    to other types. There a few things to note: (1) Floating-point numbers can
+    be converted to integers\, (2) A JSON array can be converted to a standard
+    `std::vector<short>`\, (3) A JSON object can be converted to C++
+    associative containers such as `std::unordered_map<std::string\,
+    json>`.,get__ValueType_const}
+
+    @internal
+    The idea of using a casted null pointer to choose the correct
+    implementation is from <http://stackoverflow.com/a/8315197/266378>.
+    @endinternal
+
+    @sa @ref operator ValueType() const for implicit conversion
+    @sa @ref get() for pointer-member access
+
+    @since version 1.0.0
+    */
+    template<typename ValueType, typename std::enable_if<
+                 not std::is_pointer<ValueType>::value, int>::type = 0>
+    ValueType get() const
+    {
+        return get_impl(static_cast<ValueType*>(nullptr));
+    }
+
+    /*!
+    @brief get a pointer value (explicit)
+
+    Explicit pointer access to the internally stored JSON value. No copies are
+    made.
+
+    @warning The pointer becomes invalid if the underlying JSON object
+    changes.
+
+    @tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
+    object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
+    @ref number_unsigned_t, or @ref number_float_t.
+
+    @return pointer to the internally stored JSON value if the requested
+    pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how pointers to internal values of a
+    JSON value can be requested. Note that no type conversions are made and a
+    `nullptr` is returned if the value and the requested pointer type does not
+    match.,get__PointerType}
+
+    @sa @ref get_ptr() for explicit pointer-member access
+
+    @since version 1.0.0
+    */
+    template<typename PointerType, typename std::enable_if<
+                 std::is_pointer<PointerType>::value, int>::type = 0>
+    PointerType get() noexcept
+    {
+        // delegate the call to get_ptr
+        return get_ptr<PointerType>();
+    }
+
+    /*!
+    @brief get a pointer value (explicit)
+    @copydoc get()
+    */
+    template<typename PointerType, typename std::enable_if<
+                 std::is_pointer<PointerType>::value, int>::type = 0>
+    constexpr const PointerType get() const noexcept
+    {
+        // delegate the call to get_ptr
+        return get_ptr<PointerType>();
+    }
+
+    /*!
+    @brief get a pointer value (implicit)
+
+    Implicit pointer access to the internally stored JSON value. No copies are
+    made.
+
+    @warning Writing data to the pointee of the result yields an undefined
+    state.
+
+    @tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
+    object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
+    @ref number_unsigned_t, or @ref number_float_t. Enforced by a static
+    assertion.
+
+    @return pointer to the internally stored JSON value if the requested
+    pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how pointers to internal values of a
+    JSON value can be requested. Note that no type conversions are made and a
+    `nullptr` is returned if the value and the requested pointer type does not
+    match.,get_ptr}
+
+    @since version 1.0.0
+    */
+    template<typename PointerType, typename std::enable_if<
+                 std::is_pointer<PointerType>::value, int>::type = 0>
+    PointerType get_ptr() noexcept
+    {
+        // get the type of the PointerType (remove pointer and const)
+        using pointee_t = typename std::remove_const<typename
+                          std::remove_pointer<typename
+                          std::remove_const<PointerType>::type>::type>::type;
+        // make sure the type matches the allowed types
+        static_assert(
+            std::is_same<object_t, pointee_t>::value
+            or std::is_same<array_t, pointee_t>::value
+            or std::is_same<string_t, pointee_t>::value
+            or std::is_same<boolean_t, pointee_t>::value
+            or std::is_same<number_integer_t, pointee_t>::value
+            or std::is_same<number_unsigned_t, pointee_t>::value
+            or std::is_same<number_float_t, pointee_t>::value
+            , "incompatible pointer type");
+
+        // delegate the call to get_impl_ptr<>()
+        return get_impl_ptr(static_cast<PointerType>(nullptr));
+    }
+
+    /*!
+    @brief get a pointer value (implicit)
+    @copydoc get_ptr()
+    */
+    template<typename PointerType, typename std::enable_if<
+                 std::is_pointer<PointerType>::value and
+                 std::is_const<typename std::remove_pointer<PointerType>::type>::value, int>::type = 0>
+    constexpr const PointerType get_ptr() const noexcept
+    {
+        // get the type of the PointerType (remove pointer and const)
+        using pointee_t = typename std::remove_const<typename
+                          std::remove_pointer<typename
+                          std::remove_const<PointerType>::type>::type>::type;
+        // make sure the type matches the allowed types
+        static_assert(
+            std::is_same<object_t, pointee_t>::value
+            or std::is_same<array_t, pointee_t>::value
+            or std::is_same<string_t, pointee_t>::value
+            or std::is_same<boolean_t, pointee_t>::value
+            or std::is_same<number_integer_t, pointee_t>::value
+            or std::is_same<number_unsigned_t, pointee_t>::value
+            or std::is_same<number_float_t, pointee_t>::value
+            , "incompatible pointer type");
+
+        // delegate the call to get_impl_ptr<>() const
+        return get_impl_ptr(static_cast<const PointerType>(nullptr));
+    }
+
+    /*!
+    @brief get a reference value (implicit)
+
+    Implict reference access to the internally stored JSON value. No copies
+    are made.
+
+    @warning Writing data to the referee of the result yields an undefined
+    state.
+
+    @tparam ReferenceType reference type; must be a reference to @ref array_t,
+    @ref object_t, @ref string_t, @ref boolean_t, @ref number_integer_t, or
+    @ref number_float_t. Enforced by static assertion.
+
+    @return reference to the internally stored JSON value if the requested
+    reference type @a ReferenceType fits to the JSON value; throws
+    std::domain_error otherwise
+
+    @throw std::domain_error in case passed type @a ReferenceType is
+    incompatible with the stored JSON value
+
+    @complexity Constant.
+
+    @liveexample{The example shows several calls to `get_ref()`.,get_ref}
+
+    @since version 1.1.0
+    */
+    template<typename ReferenceType, typename std::enable_if<
+                 std::is_reference<ReferenceType>::value, int>::type = 0>
+    ReferenceType get_ref()
+    {
+        // delegate call to get_ref_impl
+        return get_ref_impl<ReferenceType>(*this);
+    }
+
+    /*!
+    @brief get a reference value (implicit)
+    @copydoc get_ref()
+    */
+    template<typename ReferenceType, typename std::enable_if<
+                 std::is_reference<ReferenceType>::value and
+                 std::is_const<typename std::remove_reference<ReferenceType>::type>::value, int>::type = 0>
+    ReferenceType get_ref() const
+    {
+        // delegate call to get_ref_impl
+        return get_ref_impl<ReferenceType>(*this);
+    }
+
+    /*!
+    @brief get a value (implicit)
+
+    Implicit type conversion between the JSON value and a compatible value.
+    The call is realized by calling @ref get() const.
+
+    @tparam ValueType non-pointer type compatible to the JSON value, for
+    instance `int` for JSON integer numbers, `bool` for JSON booleans, or
+    `std::vector` types for JSON arrays. The character type of @ref string_t
+    as well as an initializer list of this type is excluded to avoid
+    ambiguities as these types implicitly convert to `std::string`.
+
+    @return copy of the JSON value, converted to type @a ValueType
+
+    @throw std::domain_error in case passed type @a ValueType is incompatible
+    to JSON, thrown by @ref get() const
+
+    @complexity Linear in the size of the JSON value.
+
+    @liveexample{The example below shows several conversions from JSON values
+    to other types. There a few things to note: (1) Floating-point numbers can
+    be converted to integers\, (2) A JSON array can be converted to a standard
+    `std::vector<short>`\, (3) A JSON object can be converted to C++
+    associative containers such as `std::unordered_map<std::string\,
+    json>`.,operator__ValueType}
+
+    @since version 1.0.0
+    */
+    template < typename ValueType, typename std::enable_if <
+                   not std::is_pointer<ValueType>::value and
+                   not std::is_same<ValueType, typename string_t::value_type>::value
+#ifndef _MSC_VER  // Fix for issue #167 operator<< abiguity under VS2015
+                   and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
+#endif
+                   , int >::type = 0 >
+    operator ValueType() const
+    {
+        // delegate the call to get<>() const
+        return get<ValueType>();
+    }
+
+    /// @}
+
+
+    ////////////////////
+    // element access //
+    ////////////////////
+
+    /// @name element access
+    /// Access to the JSON value.
+    /// @{
+
+    /*!
+    @brief access specified array element with bounds checking
+
+    Returns a reference to the element at specified location @a idx, with
+    bounds checking.
+
+    @param[in] idx  index of the element to access
+
+    @return reference to the element at index @a idx
+
+    @throw std::domain_error if the JSON value is not an array; example:
+    `"cannot use at() with string"`
+    @throw std::out_of_range if the index @a idx is out of range of the array;
+    that is, `idx >= size()`; example: `"array index 7 is out of range"`
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how array elements can be read and
+    written using `at()`.,at__size_type}
+
+    @since version 1.0.0
+    */
+    reference at(size_type idx)
+    {
+        // at only works for arrays
+        if (is_array())
+        {
+            try
+            {
+                return m_value.array->at(idx);
+            }
+            catch (std::out_of_range&)
+            {
+                // create better exception explanation
+                throw std::out_of_range("array index " + std::to_string(idx) + " is out of range");
+            }
+        }
+        else
+        {
+            throw std::domain_error("cannot use at() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief access specified array element with bounds checking
+
+    Returns a const reference to the element at specified location @a idx,
+    with bounds checking.
+
+    @param[in] idx  index of the element to access
+
+    @return const reference to the element at index @a idx
+
+    @throw std::domain_error if the JSON value is not an array; example:
+    `"cannot use at() with string"`
+    @throw std::out_of_range if the index @a idx is out of range of the array;
+    that is, `idx >= size()`; example: `"array index 7 is out of range"`
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how array elements can be read using
+    `at()`.,at__size_type_const}
+
+    @since version 1.0.0
+    */
+    const_reference at(size_type idx) const
+    {
+        // at only works for arrays
+        if (is_array())
+        {
+            try
+            {
+                return m_value.array->at(idx);
+            }
+            catch (std::out_of_range&)
+            {
+                // create better exception explanation
+                throw std::out_of_range("array index " + std::to_string(idx) + " is out of range");
+            }
+        }
+        else
+        {
+            throw std::domain_error("cannot use at() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief access specified object element with bounds checking
+
+    Returns a reference to the element at with specified key @a key, with
+    bounds checking.
+
+    @param[in] key  key of the element to access
+
+    @return reference to the element at key @a key
+
+    @throw std::domain_error if the JSON value is not an object; example:
+    `"cannot use at() with boolean"`
+    @throw std::out_of_range if the key @a key is is not stored in the object;
+    that is, `find(key) == end()`; example: `"key "the fast" not found"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be read and
+    written using `at()`.,at__object_t_key_type}
+
+    @sa @ref operator[](const typename object_t::key_type&) for unchecked
+    access by reference
+    @sa @ref value() for access by value with a default value
+
+    @since version 1.0.0
+    */
+    reference at(const typename object_t::key_type& key)
+    {
+        // at only works for objects
+        if (is_object())
+        {
+            try
+            {
+                return m_value.object->at(key);
+            }
+            catch (std::out_of_range&)
+            {
+                // create better exception explanation
+                throw std::out_of_range("key '" + key + "' not found");
+            }
+        }
+        else
+        {
+            throw std::domain_error("cannot use at() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief access specified object element with bounds checking
+
+    Returns a const reference to the element at with specified key @a key,
+    with bounds checking.
+
+    @param[in] key  key of the element to access
+
+    @return const reference to the element at key @a key
+
+    @throw std::domain_error if the JSON value is not an object; example:
+    `"cannot use at() with boolean"`
+    @throw std::out_of_range if the key @a key is is not stored in the object;
+    that is, `find(key) == end()`; example: `"key "the fast" not found"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be read using
+    `at()`.,at__object_t_key_type_const}
+
+    @sa @ref operator[](const typename object_t::key_type&) for unchecked
+    access by reference
+    @sa @ref value() for access by value with a default value
+
+    @since version 1.0.0
+    */
+    const_reference at(const typename object_t::key_type& key) const
+    {
+        // at only works for objects
+        if (is_object())
+        {
+            try
+            {
+                return m_value.object->at(key);
+            }
+            catch (std::out_of_range&)
+            {
+                // create better exception explanation
+                throw std::out_of_range("key '" + key + "' not found");
+            }
+        }
+        else
+        {
+            throw std::domain_error("cannot use at() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief access specified array element
+
+    Returns a reference to the element at specified location @a idx.
+
+    @note If @a idx is beyond the range of the array (i.e., `idx >= size()`),
+    then the array is silently filled up with `null` values to make `idx` a
+    valid reference to the last stored element.
+
+    @param[in] idx  index of the element to access
+
+    @return reference to the element at index @a idx
+
+    @throw std::domain_error if JSON is not an array or null; example:
+    `"cannot use operator[] with string"`
+
+    @complexity Constant if @a idx is in the range of the array. Otherwise
+    linear in `idx - size()`.
+
+    @liveexample{The example below shows how array elements can be read and
+    written using `[]` operator. Note the addition of `null`
+    values.,operatorarray__size_type}
+
+    @since version 1.0.0
+    */
+    reference operator[](size_type idx)
+    {
+        // implicitly convert null value to an empty array
+        if (is_null())
+        {
+            m_type = value_t::array;
+            m_value.array = create<array_t>();
+            assert_invariant();
+        }
+
+        // operator[] only works for arrays
+        if (is_array())
+        {
+            // fill up array with null values if given idx is outside range
+            if (idx >= m_value.array->size())
+            {
+                m_value.array->insert(m_value.array->end(),
+                                      idx - m_value.array->size() + 1,
+                                      basic_json());
+            }
+
+            return m_value.array->operator[](idx);
+        }
+        else
+        {
+            throw std::domain_error("cannot use operator[] with " + type_name());
+        }
+    }
+
+    /*!
+    @brief access specified array element
+
+    Returns a const reference to the element at specified location @a idx.
+
+    @param[in] idx  index of the element to access
+
+    @return const reference to the element at index @a idx
+
+    @throw std::domain_error if JSON is not an array; example: `"cannot use
+    operator[] with null"`
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how array elements can be read using
+    the `[]` operator.,operatorarray__size_type_const}
+
+    @since version 1.0.0
+    */
+    const_reference operator[](size_type idx) const
+    {
+        // const operator[] only works for arrays
+        if (is_array())
+        {
+            return m_value.array->operator[](idx);
+        }
+        else
+        {
+            throw std::domain_error("cannot use operator[] with " + type_name());
+        }
+    }
+
+    /*!
+    @brief access specified object element
+
+    Returns a reference to the element at with specified key @a key.
+
+    @note If @a key is not found in the object, then it is silently added to
+    the object and filled with a `null` value to make `key` a valid reference.
+    In case the value was `null` before, it is converted to an object.
+
+    @param[in] key  key of the element to access
+
+    @return reference to the element at key @a key
+
+    @throw std::domain_error if JSON is not an object or null; example:
+    `"cannot use operator[] with string"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be read and
+    written using the `[]` operator.,operatorarray__key_type}
+
+    @sa @ref at(const typename object_t::key_type&) for access by reference
+    with range checking
+    @sa @ref value() for access by value with a default value
+
+    @since version 1.0.0
+    */
+    reference operator[](const typename object_t::key_type& key)
+    {
+        // implicitly convert null value to an empty object
+        if (is_null())
+        {
+            m_type = value_t::object;
+            m_value.object = create<object_t>();
+            assert_invariant();
+        }
+
+        // operator[] only works for objects
+        if (is_object())
+        {
+            return m_value.object->operator[](key);
+        }
+        else
+        {
+            throw std::domain_error("cannot use operator[] with " + type_name());
+        }
+    }
+
+    /*!
+    @brief read-only access specified object element
+
+    Returns a const reference to the element at with specified key @a key. No
+    bounds checking is performed.
+
+    @warning If the element with key @a key does not exist, the behavior is
+    undefined.
+
+    @param[in] key  key of the element to access
+
+    @return const reference to the element at key @a key
+
+    @pre The element with key @a key must exist. **This precondition is
+         enforced with an assertion.**
+
+    @throw std::domain_error if JSON is not an object; example: `"cannot use
+    operator[] with null"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be read using
+    the `[]` operator.,operatorarray__key_type_const}
+
+    @sa @ref at(const typename object_t::key_type&) for access by reference
+    with range checking
+    @sa @ref value() for access by value with a default value
+
+    @since version 1.0.0
+    */
+    const_reference operator[](const typename object_t::key_type& key) const
+    {
+        // const operator[] only works for objects
+        if (is_object())
+        {
+            assert(m_value.object->find(key) != m_value.object->end());
+            return m_value.object->find(key)->second;
+        }
+        else
+        {
+            throw std::domain_error("cannot use operator[] with " + type_name());
+        }
+    }
+
+    /*!
+    @brief access specified object element
+
+    Returns a reference to the element at with specified key @a key.
+
+    @note If @a key is not found in the object, then it is silently added to
+    the object and filled with a `null` value to make `key` a valid reference.
+    In case the value was `null` before, it is converted to an object.
+
+    @param[in] key  key of the element to access
+
+    @return reference to the element at key @a key
+
+    @throw std::domain_error if JSON is not an object or null; example:
+    `"cannot use operator[] with string"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be read and
+    written using the `[]` operator.,operatorarray__key_type}
+
+    @sa @ref at(const typename object_t::key_type&) for access by reference
+    with range checking
+    @sa @ref value() for access by value with a default value
+
+    @since version 1.0.0
+    */
+    template<typename T, std::size_t n>
+    reference operator[](T * (&key)[n])
+    {
+        return operator[](static_cast<const T>(key));
+    }
+
+    /*!
+    @brief read-only access specified object element
+
+    Returns a const reference to the element at with specified key @a key. No
+    bounds checking is performed.
+
+    @warning If the element with key @a key does not exist, the behavior is
+    undefined.
+
+    @note This function is required for compatibility reasons with Clang.
+
+    @param[in] key  key of the element to access
+
+    @return const reference to the element at key @a key
+
+    @throw std::domain_error if JSON is not an object; example: `"cannot use
+    operator[] with null"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be read using
+    the `[]` operator.,operatorarray__key_type_const}
+
+    @sa @ref at(const typename object_t::key_type&) for access by reference
+    with range checking
+    @sa @ref value() for access by value with a default value
+
+    @since version 1.0.0
+    */
+    template<typename T, std::size_t n>
+    const_reference operator[](T * (&key)[n]) const
+    {
+        return operator[](static_cast<const T>(key));
+    }
+
+    /*!
+    @brief access specified object element
+
+    Returns a reference to the element at with specified key @a key.
+
+    @note If @a key is not found in the object, then it is silently added to
+    the object and filled with a `null` value to make `key` a valid reference.
+    In case the value was `null` before, it is converted to an object.
+
+    @param[in] key  key of the element to access
+
+    @return reference to the element at key @a key
+
+    @throw std::domain_error if JSON is not an object or null; example:
+    `"cannot use operator[] with string"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be read and
+    written using the `[]` operator.,operatorarray__key_type}
+
+    @sa @ref at(const typename object_t::key_type&) for access by reference
+    with range checking
+    @sa @ref value() for access by value with a default value
+
+    @since version 1.1.0
+    */
+    template<typename T>
+    reference operator[](T* key)
+    {
+        // implicitly convert null to object
+        if (is_null())
+        {
+            m_type = value_t::object;
+            m_value = value_t::object;
+            assert_invariant();
+        }
+
+        // at only works for objects
+        if (is_object())
+        {
+            return m_value.object->operator[](key);
+        }
+        else
+        {
+            throw std::domain_error("cannot use operator[] with " + type_name());
+        }
+    }
+
+    /*!
+    @brief read-only access specified object element
+
+    Returns a const reference to the element at with specified key @a key. No
+    bounds checking is performed.
+
+    @warning If the element with key @a key does not exist, the behavior is
+    undefined.
+
+    @param[in] key  key of the element to access
+
+    @return const reference to the element at key @a key
+
+    @pre The element with key @a key must exist. **This precondition is
+         enforced with an assertion.**
+
+    @throw std::domain_error if JSON is not an object; example: `"cannot use
+    operator[] with null"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be read using
+    the `[]` operator.,operatorarray__key_type_const}
+
+    @sa @ref at(const typename object_t::key_type&) for access by reference
+    with range checking
+    @sa @ref value() for access by value with a default value
+
+    @since version 1.1.0
+    */
+    template<typename T>
+    const_reference operator[](T* key) const
+    {
+        // at only works for objects
+        if (is_object())
+        {
+            assert(m_value.object->find(key) != m_value.object->end());
+            return m_value.object->find(key)->second;
+        }
+        else
+        {
+            throw std::domain_error("cannot use operator[] with " + type_name());
+        }
+    }
+
+    /*!
+    @brief access specified object element with default value
+
+    Returns either a copy of an object's element at the specified key @a key
+    or a given default value if no element with key @a key exists.
+
+    The function is basically equivalent to executing
+    @code {.cpp}
+    try {
+        return at(key);
+    } catch(std::out_of_range) {
+        return default_value;
+    }
+    @endcode
+
+    @note Unlike @ref at(const typename object_t::key_type&), this function
+    does not throw if the given key @a key was not found.
+
+    @note Unlike @ref operator[](const typename object_t::key_type& key), this
+    function does not implicitly add an element to the position defined by @a
+    key. This function is furthermore also applicable to const objects.
+
+    @param[in] key  key of the element to access
+    @param[in] default_value  the value to return if @a key is not found
+
+    @tparam ValueType type compatible to JSON values, for instance `int` for
+    JSON integer numbers, `bool` for JSON booleans, or `std::vector` types for
+    JSON arrays. Note the type of the expected value at @a key and the default
+    value @a default_value must be compatible.
+
+    @return copy of the element at key @a key or @a default_value if @a key
+    is not found
+
+    @throw std::domain_error if JSON is not an object; example: `"cannot use
+    value() with null"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be queried
+    with a default value.,basic_json__value}
+
+    @sa @ref at(const typename object_t::key_type&) for access by reference
+    with range checking
+    @sa @ref operator[](const typename object_t::key_type&) for unchecked
+    access by reference
+
+    @since version 1.0.0
+    */
+    template<class ValueType, typename std::enable_if<
+                 std::is_convertible<basic_json_t, ValueType>::value, int>::type = 0>
+    ValueType value(const typename object_t::key_type& key, ValueType default_value) const
+    {
+        // at only works for objects
+        if (is_object())
+        {
+            // if key is found, return value and given default value otherwise
+            const auto it = find(key);
+            if (it != end())
+            {
+                return *it;
+            }
+            else
+            {
+                return default_value;
+            }
+        }
+        else
+        {
+            throw std::domain_error("cannot use value() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief overload for a default value of type const char*
+    @copydoc basic_json::value(const typename object_t::key_type&, ValueType) const
+    */
+    string_t value(const typename object_t::key_type& key, const char* default_value) const
+    {
+        return value(key, string_t(default_value));
+    }
+
+    /*!
+    @brief access specified object element via JSON Pointer with default value
+
+    Returns either a copy of an object's element at the specified key @a key
+    or a given default value if no element with key @a key exists.
+
+    The function is basically equivalent to executing
+    @code {.cpp}
+    try {
+        return at(ptr);
+    } catch(std::out_of_range) {
+        return default_value;
+    }
+    @endcode
+
+    @note Unlike @ref at(const json_pointer&), this function does not throw
+    if the given key @a key was not found.
+
+    @param[in] ptr  a JSON pointer to the element to access
+    @param[in] default_value  the value to return if @a ptr found no value
+
+    @tparam ValueType type compatible to JSON values, for instance `int` for
+    JSON integer numbers, `bool` for JSON booleans, or `std::vector` types for
+    JSON arrays. Note the type of the expected value at @a key and the default
+    value @a default_value must be compatible.
+
+    @return copy of the element at key @a key or @a default_value if @a key
+    is not found
+
+    @throw std::domain_error if JSON is not an object; example: `"cannot use
+    value() with null"`
+
+    @complexity Logarithmic in the size of the container.
+
+    @liveexample{The example below shows how object elements can be queried
+    with a default value.,basic_json__value_ptr}
+
+    @sa @ref operator[](const json_pointer&) for unchecked access by reference
+
+    @since version 2.0.2
+    */
+    template<class ValueType, typename std::enable_if<
+                 std::is_convertible<basic_json_t, ValueType>::value, int>::type = 0>
+    ValueType value(const json_pointer& ptr, ValueType default_value) const
+    {
+        // at only works for objects
+        if (is_object())
+        {
+            // if pointer resolves a value, return it or use default value
+            try
+            {
+                return ptr.get_checked(this);
+            }
+            catch (std::out_of_range&)
+            {
+                return default_value;
+            }
+        }
+        else
+        {
+            throw std::domain_error("cannot use value() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief overload for a default value of type const char*
+    @copydoc basic_json::value(const json_pointer&, ValueType) const
+    */
+    string_t value(const json_pointer& ptr, const char* default_value) const
+    {
+        return value(ptr, string_t(default_value));
+    }
+
+    /*!
+    @brief access the first element
+
+    Returns a reference to the first element in the container. For a JSON
+    container `c`, the expression `c.front()` is equivalent to `*c.begin()`.
+
+    @return In case of a structured type (array or object), a reference to the
+    first element is returned. In cast of number, string, or boolean values, a
+    reference to the value is returned.
+
+    @complexity Constant.
+
+    @pre The JSON value must not be `null` (would throw `std::out_of_range`)
+    or an empty array or object (undefined behavior, **guarded by
+    assertions**).
+    @post The JSON value remains unchanged.
+
+    @throw std::out_of_range when called on `null` value
+
+    @liveexample{The following code shows an example for `front()`.,front}
+
+    @sa @ref back() -- access the last element
+
+    @since version 1.0.0
+    */
+    reference front()
+    {
+        return *begin();
+    }
+
+    /*!
+    @copydoc basic_json::front()
+    */
+    const_reference front() const
+    {
+        return *cbegin();
+    }
+
+    /*!
+    @brief access the last element
+
+    Returns a reference to the last element in the container. For a JSON
+    container `c`, the expression `c.back()` is equivalent to
+    @code {.cpp}
+    auto tmp = c.end();
+    --tmp;
+    return *tmp;
+    @endcode
+
+    @return In case of a structured type (array or object), a reference to the
+    last element is returned. In cast of number, string, or boolean values, a
+    reference to the value is returned.
+
+    @complexity Constant.
+
+    @pre The JSON value must not be `null` (would throw `std::out_of_range`)
+    or an empty array or object (undefined behavior, **guarded by
+    assertions**).
+    @post The JSON value remains unchanged.
+
+    @throw std::out_of_range when called on `null` value.
+
+    @liveexample{The following code shows an example for `back()`.,back}
+
+    @sa @ref front() -- access the first element
+
+    @since version 1.0.0
+    */
+    reference back()
+    {
+        auto tmp = end();
+        --tmp;
+        return *tmp;
+    }
+
+    /*!
+    @copydoc basic_json::back()
+    */
+    const_reference back() const
+    {
+        auto tmp = cend();
+        --tmp;
+        return *tmp;
+    }
+
+    /*!
+    @brief remove element given an iterator
+
+    Removes the element specified by iterator @a pos. The iterator @a pos must
+    be valid and dereferenceable. Thus the `end()` iterator (which is valid,
+    but is not dereferenceable) cannot be used as a value for @a pos.
+
+    If called on a primitive type other than `null`, the resulting JSON value
+    will be `null`.
+
+    @param[in] pos iterator to the element to remove
+    @return Iterator following the last removed element. If the iterator @a
+    pos refers to the last element, the `end()` iterator is returned.
+
+    @tparam IteratorType an @ref iterator or @ref const_iterator
+
+    @post Invalidates iterators and references at or after the point of the
+    erase, including the `end()` iterator.
+
+    @throw std::domain_error if called on a `null` value; example: `"cannot
+    use erase() with null"`
+    @throw std::domain_error if called on an iterator which does not belong to
+    the current JSON value; example: `"iterator does not fit current value"`
+    @throw std::out_of_range if called on a primitive type with invalid
+    iterator (i.e., any iterator which is not `begin()`); example: `"iterator
+    out of range"`
+
+    @complexity The complexity depends on the type:
+    - objects: amortized constant
+    - arrays: linear in distance between pos and the end of the container
+    - strings: linear in the length of the string
+    - other types: constant
+
+    @liveexample{The example shows the result of `erase()` for different JSON
+    types.,erase__IteratorType}
+
+    @sa @ref erase(IteratorType, IteratorType) -- removes the elements in
+    the given range
+    @sa @ref erase(const typename object_t::key_type&) -- removes the element
+    from an object at the given key
+    @sa @ref erase(const size_type) -- removes the element from an array at
+    the given index
+
+    @since version 1.0.0
+    */
+    template<class IteratorType, typename std::enable_if<
+                 std::is_same<IteratorType, typename basic_json_t::iterator>::value or
+                 std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int>::type
+             = 0>
+    IteratorType erase(IteratorType pos)
+    {
+        // make sure iterator fits the current value
+        if (this != pos.m_object)
+        {
+            throw std::domain_error("iterator does not fit current value");
+        }
+
+        IteratorType result = end();
+
+        switch (m_type)
+        {
+            case value_t::boolean:
+            case value_t::number_float:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::string:
+            {
+                if (not pos.m_it.primitive_iterator.is_begin())
+                {
+                    throw std::out_of_range("iterator out of range");
+                }
+
+                if (is_string())
+                {
+                    AllocatorType<string_t> alloc;
+                    alloc.destroy(m_value.string);
+                    alloc.deallocate(m_value.string, 1);
+                    m_value.string = nullptr;
+                }
+
+                m_type = value_t::null;
+                assert_invariant();
+                break;
+            }
+
+            case value_t::object:
+            {
+                result.m_it.object_iterator = m_value.object->erase(pos.m_it.object_iterator);
+                break;
+            }
+
+            case value_t::array:
+            {
+                result.m_it.array_iterator = m_value.array->erase(pos.m_it.array_iterator);
+                break;
+            }
+
+            default:
+            {
+                throw std::domain_error("cannot use erase() with " + type_name());
+            }
+        }
+
+        return result;
+    }
+
+    /*!
+    @brief remove elements given an iterator range
+
+    Removes the element specified by the range `[first; last)`. The iterator
+    @a first does not need to be dereferenceable if `first == last`: erasing
+    an empty range is a no-op.
+
+    If called on a primitive type other than `null`, the resulting JSON value
+    will be `null`.
+
+    @param[in] first iterator to the beginning of the range to remove
+    @param[in] last iterator past the end of the range to remove
+    @return Iterator following the last removed element. If the iterator @a
+    second refers to the last element, the `end()` iterator is returned.
+
+    @tparam IteratorType an @ref iterator or @ref const_iterator
+
+    @post Invalidates iterators and references at or after the point of the
+    erase, including the `end()` iterator.
+
+    @throw std::domain_error if called on a `null` value; example: `"cannot
+    use erase() with null"`
+    @throw std::domain_error if called on iterators which does not belong to
+    the current JSON value; example: `"iterators do not fit current value"`
+    @throw std::out_of_range if called on a primitive type with invalid
+    iterators (i.e., if `first != begin()` and `last != end()`); example:
+    `"iterators out of range"`
+
+    @complexity The complexity depends on the type:
+    - objects: `log(size()) + std::distance(first, last)`
+    - arrays: linear in the distance between @a first and @a last, plus linear
+      in the distance between @a last and end of the container
+    - strings: linear in the length of the string
+    - other types: constant
+
+    @liveexample{The example shows the result of `erase()` for different JSON
+    types.,erase__IteratorType_IteratorType}
+
+    @sa @ref erase(IteratorType) -- removes the element at a given position
+    @sa @ref erase(const typename object_t::key_type&) -- removes the element
+    from an object at the given key
+    @sa @ref erase(const size_type) -- removes the element from an array at
+    the given index
+
+    @since version 1.0.0
+    */
+    template<class IteratorType, typename std::enable_if<
+                 std::is_same<IteratorType, typename basic_json_t::iterator>::value or
+                 std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int>::type
+             = 0>
+    IteratorType erase(IteratorType first, IteratorType last)
+    {
+        // make sure iterator fits the current value
+        if (this != first.m_object or this != last.m_object)
+        {
+            throw std::domain_error("iterators do not fit current value");
+        }
+
+        IteratorType result = end();
+
+        switch (m_type)
+        {
+            case value_t::boolean:
+            case value_t::number_float:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::string:
+            {
+                if (not first.m_it.primitive_iterator.is_begin() or not last.m_it.primitive_iterator.is_end())
+                {
+                    throw std::out_of_range("iterators out of range");
+                }
+
+                if (is_string())
+                {
+                    AllocatorType<string_t> alloc;
+                    alloc.destroy(m_value.string);
+                    alloc.deallocate(m_value.string, 1);
+                    m_value.string = nullptr;
+                }
+
+                m_type = value_t::null;
+                assert_invariant();
+                break;
+            }
+
+            case value_t::object:
+            {
+                result.m_it.object_iterator = m_value.object->erase(first.m_it.object_iterator,
+                                              last.m_it.object_iterator);
+                break;
+            }
+
+            case value_t::array:
+            {
+                result.m_it.array_iterator = m_value.array->erase(first.m_it.array_iterator,
+                                             last.m_it.array_iterator);
+                break;
+            }
+
+            default:
+            {
+                throw std::domain_error("cannot use erase() with " + type_name());
+            }
+        }
+
+        return result;
+    }
+
+    /*!
+    @brief remove element from a JSON object given a key
+
+    Removes elements from a JSON object with the key value @a key.
+
+    @param[in] key value of the elements to remove
+
+    @return Number of elements removed. If @a ObjectType is the default
+    `std::map` type, the return value will always be `0` (@a key was not
+    found) or `1` (@a key was found).
+
+    @post References and iterators to the erased elements are invalidated.
+    Other references and iterators are not affected.
+
+    @throw std::domain_error when called on a type other than JSON object;
+    example: `"cannot use erase() with null"`
+
+    @complexity `log(size()) + count(key)`
+
+    @liveexample{The example shows the effect of `erase()`.,erase__key_type}
+
+    @sa @ref erase(IteratorType) -- removes the element at a given position
+    @sa @ref erase(IteratorType, IteratorType) -- removes the elements in
+    the given range
+    @sa @ref erase(const size_type) -- removes the element from an array at
+    the given index
+
+    @since version 1.0.0
+    */
+    size_type erase(const typename object_t::key_type& key)
+    {
+        // this erase only works for objects
+        if (is_object())
+        {
+            return m_value.object->erase(key);
+        }
+        else
+        {
+            throw std::domain_error("cannot use erase() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief remove element from a JSON array given an index
+
+    Removes element from a JSON array at the index @a idx.
+
+    @param[in] idx index of the element to remove
+
+    @throw std::domain_error when called on a type other than JSON array;
+    example: `"cannot use erase() with null"`
+    @throw std::out_of_range when `idx >= size()`; example: `"array index 17
+    is out of range"`
+
+    @complexity Linear in distance between @a idx and the end of the container.
+
+    @liveexample{The example shows the effect of `erase()`.,erase__size_type}
+
+    @sa @ref erase(IteratorType) -- removes the element at a given position
+    @sa @ref erase(IteratorType, IteratorType) -- removes the elements in
+    the given range
+    @sa @ref erase(const typename object_t::key_type&) -- removes the element
+    from an object at the given key
+
+    @since version 1.0.0
+    */
+    void erase(const size_type idx)
+    {
+        // this erase only works for arrays
+        if (is_array())
+        {
+            if (idx >= size())
+            {
+                throw std::out_of_range("array index " + std::to_string(idx) + " is out of range");
+            }
+
+            m_value.array->erase(m_value.array->begin() + static_cast<difference_type>(idx));
+        }
+        else
+        {
+            throw std::domain_error("cannot use erase() with " + type_name());
+        }
+    }
+
+    /// @}
+
+
+    ////////////
+    // lookup //
+    ////////////
+
+    /// @name lookup
+    /// @{
+
+    /*!
+    @brief find an element in a JSON object
+
+    Finds an element in a JSON object with key equivalent to @a key. If the
+    element is not found or the JSON value is not an object, end() is
+    returned.
+
+    @param[in] key key value of the element to search for
+
+    @return Iterator to an element with key equivalent to @a key. If no such
+    element is found, past-the-end (see end()) iterator is returned.
+
+    @complexity Logarithmic in the size of the JSON object.
+
+    @liveexample{The example shows how `find()` is used.,find__key_type}
+
+    @since version 1.0.0
+    */
+    iterator find(typename object_t::key_type key)
+    {
+        auto result = end();
+
+        if (is_object())
+        {
+            result.m_it.object_iterator = m_value.object->find(key);
+        }
+
+        return result;
+    }
+
+    /*!
+    @brief find an element in a JSON object
+    @copydoc find(typename object_t::key_type)
+    */
+    const_iterator find(typename object_t::key_type key) const
+    {
+        auto result = cend();
+
+        if (is_object())
+        {
+            result.m_it.object_iterator = m_value.object->find(key);
+        }
+
+        return result;
+    }
+
+    /*!
+    @brief returns the number of occurrences of a key in a JSON object
+
+    Returns the number of elements with key @a key. If ObjectType is the
+    default `std::map` type, the return value will always be `0` (@a key was
+    not found) or `1` (@a key was found).
+
+    @param[in] key key value of the element to count
+
+    @return Number of elements with key @a key. If the JSON value is not an
+    object, the return value will be `0`.
+
+    @complexity Logarithmic in the size of the JSON object.
+
+    @liveexample{The example shows how `count()` is used.,count}
+
+    @since version 1.0.0
+    */
+    size_type count(typename object_t::key_type key) const
+    {
+        // return 0 for all nonobject types
+        return is_object() ? m_value.object->count(key) : 0;
+    }
+
+    /// @}
+
+
+    ///////////////
+    // iterators //
+    ///////////////
+
+    /// @name iterators
+    /// @{
+
+    /*!
+    @brief returns an iterator to the first element
+
+    Returns an iterator to the first element.
+
+    @image html range-begin-end.svg "Illustration from cppreference.com"
+
+    @return iterator to the first element
+
+    @complexity Constant.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is constant.
+
+    @liveexample{The following code shows an example for `begin()`.,begin}
+
+    @sa @ref cbegin() -- returns a const iterator to the beginning
+    @sa @ref end() -- returns an iterator to the end
+    @sa @ref cend() -- returns a const iterator to the end
+
+    @since version 1.0.0
+    */
+    iterator begin() noexcept
+    {
+        iterator result(this);
+        result.set_begin();
+        return result;
+    }
+
+    /*!
+    @copydoc basic_json::cbegin()
+    */
+    const_iterator begin() const noexcept
+    {
+        return cbegin();
+    }
+
+    /*!
+    @brief returns a const iterator to the first element
+
+    Returns a const iterator to the first element.
+
+    @image html range-begin-end.svg "Illustration from cppreference.com"
+
+    @return const iterator to the first element
+
+    @complexity Constant.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of `const_cast<const basic_json&>(*this).begin()`.
+
+    @liveexample{The following code shows an example for `cbegin()`.,cbegin}
+
+    @sa @ref begin() -- returns an iterator to the beginning
+    @sa @ref end() -- returns an iterator to the end
+    @sa @ref cend() -- returns a const iterator to the end
+
+    @since version 1.0.0
+    */
+    const_iterator cbegin() const noexcept
+    {
+        const_iterator result(this);
+        result.set_begin();
+        return result;
+    }
+
+    /*!
+    @brief returns an iterator to one past the last element
+
+    Returns an iterator to one past the last element.
+
+    @image html range-begin-end.svg "Illustration from cppreference.com"
+
+    @return iterator one past the last element
+
+    @complexity Constant.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is constant.
+
+    @liveexample{The following code shows an example for `end()`.,end}
+
+    @sa @ref cend() -- returns a const iterator to the end
+    @sa @ref begin() -- returns an iterator to the beginning
+    @sa @ref cbegin() -- returns a const iterator to the beginning
+
+    @since version 1.0.0
+    */
+    iterator end() noexcept
+    {
+        iterator result(this);
+        result.set_end();
+        return result;
+    }
+
+    /*!
+    @copydoc basic_json::cend()
+    */
+    const_iterator end() const noexcept
+    {
+        return cend();
+    }
+
+    /*!
+    @brief returns a const iterator to one past the last element
+
+    Returns a const iterator to one past the last element.
+
+    @image html range-begin-end.svg "Illustration from cppreference.com"
+
+    @return const iterator one past the last element
+
+    @complexity Constant.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of `const_cast<const basic_json&>(*this).end()`.
+
+    @liveexample{The following code shows an example for `cend()`.,cend}
+
+    @sa @ref end() -- returns an iterator to the end
+    @sa @ref begin() -- returns an iterator to the beginning
+    @sa @ref cbegin() -- returns a const iterator to the beginning
+
+    @since version 1.0.0
+    */
+    const_iterator cend() const noexcept
+    {
+        const_iterator result(this);
+        result.set_end();
+        return result;
+    }
+
+    /*!
+    @brief returns an iterator to the reverse-beginning
+
+    Returns an iterator to the reverse-beginning; that is, the last element.
+
+    @image html range-rbegin-rend.svg "Illustration from cppreference.com"
+
+    @complexity Constant.
+
+    @requirement This function helps `basic_json` satisfying the
+    [ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of `reverse_iterator(end())`.
+
+    @liveexample{The following code shows an example for `rbegin()`.,rbegin}
+
+    @sa @ref crbegin() -- returns a const reverse iterator to the beginning
+    @sa @ref rend() -- returns a reverse iterator to the end
+    @sa @ref crend() -- returns a const reverse iterator to the end
+
+    @since version 1.0.0
+    */
+    reverse_iterator rbegin() noexcept
+    {
+        return reverse_iterator(end());
+    }
+
+    /*!
+    @copydoc basic_json::crbegin()
+    */
+    const_reverse_iterator rbegin() const noexcept
+    {
+        return crbegin();
+    }
+
+    /*!
+    @brief returns an iterator to the reverse-end
+
+    Returns an iterator to the reverse-end; that is, one before the first
+    element.
+
+    @image html range-rbegin-rend.svg "Illustration from cppreference.com"
+
+    @complexity Constant.
+
+    @requirement This function helps `basic_json` satisfying the
+    [ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of `reverse_iterator(begin())`.
+
+    @liveexample{The following code shows an example for `rend()`.,rend}
+
+    @sa @ref crend() -- returns a const reverse iterator to the end
+    @sa @ref rbegin() -- returns a reverse iterator to the beginning
+    @sa @ref crbegin() -- returns a const reverse iterator to the beginning
+
+    @since version 1.0.0
+    */
+    reverse_iterator rend() noexcept
+    {
+        return reverse_iterator(begin());
+    }
+
+    /*!
+    @copydoc basic_json::crend()
+    */
+    const_reverse_iterator rend() const noexcept
+    {
+        return crend();
+    }
+
+    /*!
+    @brief returns a const reverse iterator to the last element
+
+    Returns a const iterator to the reverse-beginning; that is, the last
+    element.
+
+    @image html range-rbegin-rend.svg "Illustration from cppreference.com"
+
+    @complexity Constant.
+
+    @requirement This function helps `basic_json` satisfying the
+    [ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of `const_cast<const basic_json&>(*this).rbegin()`.
+
+    @liveexample{The following code shows an example for `crbegin()`.,crbegin}
+
+    @sa @ref rbegin() -- returns a reverse iterator to the beginning
+    @sa @ref rend() -- returns a reverse iterator to the end
+    @sa @ref crend() -- returns a const reverse iterator to the end
+
+    @since version 1.0.0
+    */
+    const_reverse_iterator crbegin() const noexcept
+    {
+        return const_reverse_iterator(cend());
+    }
+
+    /*!
+    @brief returns a const reverse iterator to one before the first
+
+    Returns a const reverse iterator to the reverse-end; that is, one before
+    the first element.
+
+    @image html range-rbegin-rend.svg "Illustration from cppreference.com"
+
+    @complexity Constant.
+
+    @requirement This function helps `basic_json` satisfying the
+    [ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of `const_cast<const basic_json&>(*this).rend()`.
+
+    @liveexample{The following code shows an example for `crend()`.,crend}
+
+    @sa @ref rend() -- returns a reverse iterator to the end
+    @sa @ref rbegin() -- returns a reverse iterator to the beginning
+    @sa @ref crbegin() -- returns a const reverse iterator to the beginning
+
+    @since version 1.0.0
+    */
+    const_reverse_iterator crend() const noexcept
+    {
+        return const_reverse_iterator(cbegin());
+    }
+
+  private:
+    // forward declaration
+    template<typename IteratorType> class iteration_proxy;
+
+  public:
+    /*!
+    @brief wrapper to access iterator member functions in range-based for
+
+    This function allows to access @ref iterator::key() and @ref
+    iterator::value() during range-based for loops. In these loops, a
+    reference to the JSON values is returned, so there is no access to the
+    underlying iterator.
+
+    @note The name of this function is not yet final and may change in the
+    future.
+    */
+    static iteration_proxy<iterator> iterator_wrapper(reference cont)
+    {
+        return iteration_proxy<iterator>(cont);
+    }
+
+    /*!
+    @copydoc iterator_wrapper(reference)
+    */
+    static iteration_proxy<const_iterator> iterator_wrapper(const_reference cont)
+    {
+        return iteration_proxy<const_iterator>(cont);
+    }
+
+    /// @}
+
+
+    //////////////
+    // capacity //
+    //////////////
+
+    /// @name capacity
+    /// @{
+
+    /*!
+    @brief checks whether the container is empty
+
+    Checks if a JSON value has no elements.
+
+    @return The return value depends on the different types and is
+            defined as follows:
+            Value type  | return value
+            ----------- | -------------
+            null        | `true`
+            boolean     | `false`
+            string      | `false`
+            number      | `false`
+            object      | result of function `object_t::empty()`
+            array       | result of function `array_t::empty()`
+
+    @note This function does not return whether a string stored as JSON value
+    is empty - it returns whether the JSON container itself is empty which is
+    false in the case of a string.
+
+    @complexity Constant, as long as @ref array_t and @ref object_t satisfy
+    the Container concept; that is, their `empty()` functions have constant
+    complexity.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of `begin() == end()`.
+
+    @liveexample{The following code uses `empty()` to check if a JSON
+    object contains any elements.,empty}
+
+    @sa @ref size() -- returns the number of elements
+
+    @since version 1.0.0
+    */
+    bool empty() const noexcept
+    {
+        switch (m_type)
+        {
+            case value_t::null:
+            {
+                // null values are empty
+                return true;
+            }
+
+            case value_t::array:
+            {
+                // delegate call to array_t::empty()
+                return m_value.array->empty();
+            }
+
+            case value_t::object:
+            {
+                // delegate call to object_t::empty()
+                return m_value.object->empty();
+            }
+
+            default:
+            {
+                // all other types are nonempty
+                return false;
+            }
+        }
+    }
+
+    /*!
+    @brief returns the number of elements
+
+    Returns the number of elements in a JSON value.
+
+    @return The return value depends on the different types and is
+            defined as follows:
+            Value type  | return value
+            ----------- | -------------
+            null        | `0`
+            boolean     | `1`
+            string      | `1`
+            number      | `1`
+            object      | result of function object_t::size()
+            array       | result of function array_t::size()
+
+    @note This function does not return the length of a string stored as JSON
+    value - it returns the number of elements in the JSON value which is 1 in
+    the case of a string.
+
+    @complexity Constant, as long as @ref array_t and @ref object_t satisfy
+    the Container concept; that is, their size() functions have constant
+    complexity.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of `std::distance(begin(), end())`.
+
+    @liveexample{The following code calls `size()` on the different value
+    types.,size}
+
+    @sa @ref empty() -- checks whether the container is empty
+    @sa @ref max_size() -- returns the maximal number of elements
+
+    @since version 1.0.0
+    */
+    size_type size() const noexcept
+    {
+        switch (m_type)
+        {
+            case value_t::null:
+            {
+                // null values are empty
+                return 0;
+            }
+
+            case value_t::array:
+            {
+                // delegate call to array_t::size()
+                return m_value.array->size();
+            }
+
+            case value_t::object:
+            {
+                // delegate call to object_t::size()
+                return m_value.object->size();
+            }
+
+            default:
+            {
+                // all other types have size 1
+                return 1;
+            }
+        }
+    }
+
+    /*!
+    @brief returns the maximum possible number of elements
+
+    Returns the maximum number of elements a JSON value is able to hold due to
+    system or library implementation limitations, i.e. `std::distance(begin(),
+    end())` for the JSON value.
+
+    @return The return value depends on the different types and is
+            defined as follows:
+            Value type  | return value
+            ----------- | -------------
+            null        | `0` (same as `size()`)
+            boolean     | `1` (same as `size()`)
+            string      | `1` (same as `size()`)
+            number      | `1` (same as `size()`)
+            object      | result of function `object_t::max_size()`
+            array       | result of function `array_t::max_size()`
+
+    @complexity Constant, as long as @ref array_t and @ref object_t satisfy
+    the Container concept; that is, their `max_size()` functions have constant
+    complexity.
+
+    @requirement This function helps `basic_json` satisfying the
+    [Container](http://en.cppreference.com/w/cpp/concept/Container)
+    requirements:
+    - The complexity is constant.
+    - Has the semantics of returning `b.size()` where `b` is the largest
+      possible JSON value.
+
+    @liveexample{The following code calls `max_size()` on the different value
+    types. Note the output is implementation specific.,max_size}
+
+    @sa @ref size() -- returns the number of elements
+
+    @since version 1.0.0
+    */
+    size_type max_size() const noexcept
+    {
+        switch (m_type)
+        {
+            case value_t::array:
+            {
+                // delegate call to array_t::max_size()
+                return m_value.array->max_size();
+            }
+
+            case value_t::object:
+            {
+                // delegate call to object_t::max_size()
+                return m_value.object->max_size();
+            }
+
+            default:
+            {
+                // all other types have max_size() == size()
+                return size();
+            }
+        }
+    }
+
+    /// @}
+
+
+    ///////////////
+    // modifiers //
+    ///////////////
+
+    /// @name modifiers
+    /// @{
+
+    /*!
+    @brief clears the contents
+
+    Clears the content of a JSON value and resets it to the default value as
+    if @ref basic_json(value_t) would have been called:
+
+    Value type  | initial value
+    ----------- | -------------
+    null        | `null`
+    boolean     | `false`
+    string      | `""`
+    number      | `0`
+    object      | `{}`
+    array       | `[]`
+
+    @note Floating-point numbers are set to `0.0` which will be serialized to
+    `0`. The vale type remains @ref number_float_t.
+
+    @complexity Linear in the size of the JSON value.
+
+    @liveexample{The example below shows the effect of `clear()` to different
+    JSON types.,clear}
+
+    @since version 1.0.0
+    */
+    void clear() noexcept
+    {
+        switch (m_type)
+        {
+            case value_t::number_integer:
+            {
+                m_value.number_integer = 0;
+                break;
+            }
+
+            case value_t::number_unsigned:
+            {
+                m_value.number_unsigned = 0;
+                break;
+            }
+
+            case value_t::number_float:
+            {
+                m_value.number_float = 0.0;
+                break;
+            }
+
+            case value_t::boolean:
+            {
+                m_value.boolean = false;
+                break;
+            }
+
+            case value_t::string:
+            {
+                m_value.string->clear();
+                break;
+            }
+
+            case value_t::array:
+            {
+                m_value.array->clear();
+                break;
+            }
+
+            case value_t::object:
+            {
+                m_value.object->clear();
+                break;
+            }
+
+            default:
+            {
+                break;
+            }
+        }
+    }
+
+    /*!
+    @brief add an object to an array
+
+    Appends the given element @a val to the end of the JSON value. If the
+    function is called on a JSON null value, an empty array is created before
+    appending @a val.
+
+    @param[in] val the value to add to the JSON array
+
+    @throw std::domain_error when called on a type other than JSON array or
+    null; example: `"cannot use push_back() with number"`
+
+    @complexity Amortized constant.
+
+    @liveexample{The example shows how `push_back()` and `+=` can be used to
+    add elements to a JSON array. Note how the `null` value was silently
+    converted to a JSON array.,push_back}
+
+    @since version 1.0.0
+    */
+    void push_back(basic_json&& val)
+    {
+        // push_back only works for null objects or arrays
+        if (not(is_null() or is_array()))
+        {
+            throw std::domain_error("cannot use push_back() with " + type_name());
+        }
+
+        // transform null object into an array
+        if (is_null())
+        {
+            m_type = value_t::array;
+            m_value = value_t::array;
+            assert_invariant();
+        }
+
+        // add element to array (move semantics)
+        m_value.array->push_back(std::move(val));
+        // invalidate object
+        val.m_type = value_t::null;
+    }
+
+    /*!
+    @brief add an object to an array
+    @copydoc push_back(basic_json&&)
+    */
+    reference operator+=(basic_json&& val)
+    {
+        push_back(std::move(val));
+        return *this;
+    }
+
+    /*!
+    @brief add an object to an array
+    @copydoc push_back(basic_json&&)
+    */
+    void push_back(const basic_json& val)
+    {
+        // push_back only works for null objects or arrays
+        if (not(is_null() or is_array()))
+        {
+            throw std::domain_error("cannot use push_back() with " + type_name());
+        }
+
+        // transform null object into an array
+        if (is_null())
+        {
+            m_type = value_t::array;
+            m_value = value_t::array;
+            assert_invariant();
+        }
+
+        // add element to array
+        m_value.array->push_back(val);
+    }
+
+    /*!
+    @brief add an object to an array
+    @copydoc push_back(basic_json&&)
+    */
+    reference operator+=(const basic_json& val)
+    {
+        push_back(val);
+        return *this;
+    }
+
+    /*!
+    @brief add an object to an object
+
+    Inserts the given element @a val to the JSON object. If the function is
+    called on a JSON null value, an empty object is created before inserting
+    @a val.
+
+    @param[in] val the value to add to the JSON object
+
+    @throw std::domain_error when called on a type other than JSON object or
+    null; example: `"cannot use push_back() with number"`
+
+    @complexity Logarithmic in the size of the container, O(log(`size()`)).
+
+    @liveexample{The example shows how `push_back()` and `+=` can be used to
+    add elements to a JSON object. Note how the `null` value was silently
+    converted to a JSON object.,push_back__object_t__value}
+
+    @since version 1.0.0
+    */
+    void push_back(const typename object_t::value_type& val)
+    {
+        // push_back only works for null objects or objects
+        if (not(is_null() or is_object()))
+        {
+            throw std::domain_error("cannot use push_back() with " + type_name());
+        }
+
+        // transform null object into an object
+        if (is_null())
+        {
+            m_type = value_t::object;
+            m_value = value_t::object;
+            assert_invariant();
+        }
+
+        // add element to array
+        m_value.object->insert(val);
+    }
+
+    /*!
+    @brief add an object to an object
+    @copydoc push_back(const typename object_t::value_type&)
+    */
+    reference operator+=(const typename object_t::value_type& val)
+    {
+        push_back(val);
+        return *this;
+    }
+
+    /*!
+    @brief add an object to an object
+
+    This function allows to use `push_back` with an initializer list. In case
+
+    1. the current value is an object,
+    2. the initializer list @a init contains only two elements, and
+    3. the first element of @a init is a string,
+
+    @a init is converted into an object element and added using
+    @ref push_back(const typename object_t::value_type&). Otherwise, @a init
+    is converted to a JSON value and added using @ref push_back(basic_json&&).
+
+    @param init  an initializer list
+
+    @complexity Linear in the size of the initializer list @a init.
+
+    @note This function is required to resolve an ambiguous overload error,
+          because pairs like `{"key", "value"}` can be both interpreted as
+          `object_t::value_type` or `std::initializer_list<basic_json>`, see
+          https://github.com/nlohmann/json/issues/235 for more information.
+
+    @liveexample{The example shows how initializer lists are treated as
+    objects when possible.,push_back__initializer_list}
+    */
+    void push_back(std::initializer_list<basic_json> init)
+    {
+        if (is_object() and init.size() == 2 and init.begin()->is_string())
+        {
+            const string_t key = *init.begin();
+            push_back(typename object_t::value_type(key, *(init.begin() + 1)));
+        }
+        else
+        {
+            push_back(basic_json(init));
+        }
+    }
+
+    /*!
+    @brief add an object to an object
+    @copydoc push_back(std::initializer_list<basic_json>)
+    */
+    reference operator+=(std::initializer_list<basic_json> init)
+    {
+        push_back(init);
+        return *this;
+    }
+
+    /*!
+    @brief inserts element
+
+    Inserts element @a val before iterator @a pos.
+
+    @param[in] pos iterator before which the content will be inserted; may be
+    the end() iterator
+    @param[in] val element to insert
+    @return iterator pointing to the inserted @a val.
+
+    @throw std::domain_error if called on JSON values other than arrays;
+    example: `"cannot use insert() with string"`
+    @throw std::domain_error if @a pos is not an iterator of *this; example:
+    `"iterator does not fit current value"`
+
+    @complexity Constant plus linear in the distance between pos and end of the
+    container.
+
+    @liveexample{The example shows how `insert()` is used.,insert}
+
+    @since version 1.0.0
+    */
+    iterator insert(const_iterator pos, const basic_json& val)
+    {
+        // insert only works for arrays
+        if (is_array())
+        {
+            // check if iterator pos fits to this JSON value
+            if (pos.m_object != this)
+            {
+                throw std::domain_error("iterator does not fit current value");
+            }
+
+            // insert to array and return iterator
+            iterator result(this);
+            result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, val);
+            return result;
+        }
+        else
+        {
+            throw std::domain_error("cannot use insert() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief inserts element
+    @copydoc insert(const_iterator, const basic_json&)
+    */
+    iterator insert(const_iterator pos, basic_json&& val)
+    {
+        return insert(pos, val);
+    }
+
+    /*!
+    @brief inserts elements
+
+    Inserts @a cnt copies of @a val before iterator @a pos.
+
+    @param[in] pos iterator before which the content will be inserted; may be
+    the end() iterator
+    @param[in] cnt number of copies of @a val to insert
+    @param[in] val element to insert
+    @return iterator pointing to the first element inserted, or @a pos if
+    `cnt==0`
+
+    @throw std::domain_error if called on JSON values other than arrays;
+    example: `"cannot use insert() with string"`
+    @throw std::domain_error if @a pos is not an iterator of *this; example:
+    `"iterator does not fit current value"`
+
+    @complexity Linear in @a cnt plus linear in the distance between @a pos
+    and end of the container.
+
+    @liveexample{The example shows how `insert()` is used.,insert__count}
+
+    @since version 1.0.0
+    */
+    iterator insert(const_iterator pos, size_type cnt, const basic_json& val)
+    {
+        // insert only works for arrays
+        if (is_array())
+        {
+            // check if iterator pos fits to this JSON value
+            if (pos.m_object != this)
+            {
+                throw std::domain_error("iterator does not fit current value");
+            }
+
+            // insert to array and return iterator
+            iterator result(this);
+            result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, cnt, val);
+            return result;
+        }
+        else
+        {
+            throw std::domain_error("cannot use insert() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief inserts elements
+
+    Inserts elements from range `[first, last)` before iterator @a pos.
+
+    @param[in] pos iterator before which the content will be inserted; may be
+    the end() iterator
+    @param[in] first begin of the range of elements to insert
+    @param[in] last end of the range of elements to insert
+
+    @throw std::domain_error if called on JSON values other than arrays;
+    example: `"cannot use insert() with string"`
+    @throw std::domain_error if @a pos is not an iterator of *this; example:
+    `"iterator does not fit current value"`
+    @throw std::domain_error if @a first and @a last do not belong to the same
+    JSON value; example: `"iterators do not fit"`
+    @throw std::domain_error if @a first or @a last are iterators into
+    container for which insert is called; example: `"passed iterators may not
+    belong to container"`
+
+    @return iterator pointing to the first element inserted, or @a pos if
+    `first==last`
+
+    @complexity Linear in `std::distance(first, last)` plus linear in the
+    distance between @a pos and end of the container.
+
+    @liveexample{The example shows how `insert()` is used.,insert__range}
+
+    @since version 1.0.0
+    */
+    iterator insert(const_iterator pos, const_iterator first, const_iterator last)
+    {
+        // insert only works for arrays
+        if (not is_array())
+        {
+            throw std::domain_error("cannot use insert() with " + type_name());
+        }
+
+        // check if iterator pos fits to this JSON value
+        if (pos.m_object != this)
+        {
+            throw std::domain_error("iterator does not fit current value");
+        }
+
+        // check if range iterators belong to the same JSON object
+        if (first.m_object != last.m_object)
+        {
+            throw std::domain_error("iterators do not fit");
+        }
+
+        if (first.m_object == this or last.m_object == this)
+        {
+            throw std::domain_error("passed iterators may not belong to container");
+        }
+
+        // insert to array and return iterator
+        iterator result(this);
+        result.m_it.array_iterator = m_value.array->insert(
+                                         pos.m_it.array_iterator,
+                                         first.m_it.array_iterator,
+                                         last.m_it.array_iterator);
+        return result;
+    }
+
+    /*!
+    @brief inserts elements
+
+    Inserts elements from initializer list @a ilist before iterator @a pos.
+
+    @param[in] pos iterator before which the content will be inserted; may be
+    the end() iterator
+    @param[in] ilist initializer list to insert the values from
+
+    @throw std::domain_error if called on JSON values other than arrays;
+    example: `"cannot use insert() with string"`
+    @throw std::domain_error if @a pos is not an iterator of *this; example:
+    `"iterator does not fit current value"`
+
+    @return iterator pointing to the first element inserted, or @a pos if
+    `ilist` is empty
+
+    @complexity Linear in `ilist.size()` plus linear in the distance between
+    @a pos and end of the container.
+
+    @liveexample{The example shows how `insert()` is used.,insert__ilist}
+
+    @since version 1.0.0
+    */
+    iterator insert(const_iterator pos, std::initializer_list<basic_json> ilist)
+    {
+        // insert only works for arrays
+        if (not is_array())
+        {
+            throw std::domain_error("cannot use insert() with " + type_name());
+        }
+
+        // check if iterator pos fits to this JSON value
+        if (pos.m_object != this)
+        {
+            throw std::domain_error("iterator does not fit current value");
+        }
+
+        // insert to array and return iterator
+        iterator result(this);
+        result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, ilist);
+        return result;
+    }
+
+    /*!
+    @brief exchanges the values
+
+    Exchanges the contents of the JSON value with those of @a other. Does not
+    invoke any move, copy, or swap operations on individual elements. All
+    iterators and references remain valid. The past-the-end iterator is
+    invalidated.
+
+    @param[in,out] other JSON value to exchange the contents with
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how JSON values can be swapped with
+    `swap()`.,swap__reference}
+
+    @since version 1.0.0
+    */
+    void swap(reference other) noexcept (
+        std::is_nothrow_move_constructible<value_t>::value and
+        std::is_nothrow_move_assignable<value_t>::value and
+        std::is_nothrow_move_constructible<json_value>::value and
+        std::is_nothrow_move_assignable<json_value>::value
+    )
+    {
+        std::swap(m_type, other.m_type);
+        std::swap(m_value, other.m_value);
+        assert_invariant();
+    }
+
+    /*!
+    @brief exchanges the values
+
+    Exchanges the contents of a JSON array with those of @a other. Does not
+    invoke any move, copy, or swap operations on individual elements. All
+    iterators and references remain valid. The past-the-end iterator is
+    invalidated.
+
+    @param[in,out] other array to exchange the contents with
+
+    @throw std::domain_error when JSON value is not an array; example: `"cannot
+    use swap() with string"`
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how arrays can be swapped with
+    `swap()`.,swap__array_t}
+
+    @since version 1.0.0
+    */
+    void swap(array_t& other)
+    {
+        // swap only works for arrays
+        if (is_array())
+        {
+            std::swap(*(m_value.array), other);
+        }
+        else
+        {
+            throw std::domain_error("cannot use swap() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief exchanges the values
+
+    Exchanges the contents of a JSON object with those of @a other. Does not
+    invoke any move, copy, or swap operations on individual elements. All
+    iterators and references remain valid. The past-the-end iterator is
+    invalidated.
+
+    @param[in,out] other object to exchange the contents with
+
+    @throw std::domain_error when JSON value is not an object; example:
+    `"cannot use swap() with string"`
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how objects can be swapped with
+    `swap()`.,swap__object_t}
+
+    @since version 1.0.0
+    */
+    void swap(object_t& other)
+    {
+        // swap only works for objects
+        if (is_object())
+        {
+            std::swap(*(m_value.object), other);
+        }
+        else
+        {
+            throw std::domain_error("cannot use swap() with " + type_name());
+        }
+    }
+
+    /*!
+    @brief exchanges the values
+
+    Exchanges the contents of a JSON string with those of @a other. Does not
+    invoke any move, copy, or swap operations on individual elements. All
+    iterators and references remain valid. The past-the-end iterator is
+    invalidated.
+
+    @param[in,out] other string to exchange the contents with
+
+    @throw std::domain_error when JSON value is not a string; example: `"cannot
+    use swap() with boolean"`
+
+    @complexity Constant.
+
+    @liveexample{The example below shows how strings can be swapped with
+    `swap()`.,swap__string_t}
+
+    @since version 1.0.0
+    */
+    void swap(string_t& other)
+    {
+        // swap only works for strings
+        if (is_string())
+        {
+            std::swap(*(m_value.string), other);
+        }
+        else
+        {
+            throw std::domain_error("cannot use swap() with " + type_name());
+        }
+    }
+
+    /// @}
+
+
+    //////////////////////////////////////////
+    // lexicographical comparison operators //
+    //////////////////////////////////////////
+
+    /// @name lexicographical comparison operators
+    /// @{
+
+  private:
+    /*!
+    @brief comparison operator for JSON types
+
+    Returns an ordering that is similar to Python:
+    - order: null < boolean < number < object < array < string
+    - furthermore, each type is not smaller than itself
+
+    @since version 1.0.0
+    */
+    friend bool operator<(const value_t lhs, const value_t rhs) noexcept
+    {
+        static constexpr std::array<uint8_t, 8> order = {{
+                0, // null
+                3, // object
+                4, // array
+                5, // string
+                1, // boolean
+                2, // integer
+                2, // unsigned
+                2, // float
+            }
+        };
+
+        // discarded values are not comparable
+        if (lhs == value_t::discarded or rhs == value_t::discarded)
+        {
+            return false;
+        }
+
+        return order[static_cast<std::size_t>(lhs)] < order[static_cast<std::size_t>(rhs)];
+    }
+
+  public:
+    /*!
+    @brief comparison: equal
+
+    Compares two JSON values for equality according to the following rules:
+    - Two JSON values are equal if (1) they are from the same type and (2)
+      their stored values are the same.
+    - Integer and floating-point numbers are automatically converted before
+      comparison. Floating-point numbers are compared indirectly: two
+      floating-point numbers `f1` and `f2` are considered equal if neither
+      `f1 > f2` nor `f2 > f1` holds.
+    - Two JSON null values are equal.
+
+    @param[in] lhs  first JSON value to consider
+    @param[in] rhs  second JSON value to consider
+    @return whether the values @a lhs and @a rhs are equal
+
+    @complexity Linear.
+
+    @liveexample{The example demonstrates comparing several JSON
+    types.,operator__equal}
+
+    @since version 1.0.0
+    */
+    friend bool operator==(const_reference lhs, const_reference rhs) noexcept
+    {
+        const auto lhs_type = lhs.type();
+        const auto rhs_type = rhs.type();
+
+        if (lhs_type == rhs_type)
+        {
+            switch (lhs_type)
+            {
+                case value_t::array:
+                {
+                    return *lhs.m_value.array == *rhs.m_value.array;
+                }
+                case value_t::object:
+                {
+                    return *lhs.m_value.object == *rhs.m_value.object;
+                }
+                case value_t::null:
+                {
+                    return true;
+                }
+                case value_t::string:
+                {
+                    return *lhs.m_value.string == *rhs.m_value.string;
+                }
+                case value_t::boolean:
+                {
+                    return lhs.m_value.boolean == rhs.m_value.boolean;
+                }
+                case value_t::number_integer:
+                {
+                    return lhs.m_value.number_integer == rhs.m_value.number_integer;
+                }
+                case value_t::number_unsigned:
+                {
+                    return lhs.m_value.number_unsigned == rhs.m_value.number_unsigned;
+                }
+                case value_t::number_float:
+                {
+                    return lhs.m_value.number_float == rhs.m_value.number_float;
+                }
+                default:
+                {
+                    return false;
+                }
+            }
+        }
+        else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
+        {
+            return static_cast<number_float_t>(lhs.m_value.number_integer) == rhs.m_value.number_float;
+        }
+        else if (lhs_type == value_t::number_float and rhs_type == value_t::number_integer)
+        {
+            return lhs.m_value.number_float == static_cast<number_float_t>(rhs.m_value.number_integer);
+        }
+        else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_float)
+        {
+            return static_cast<number_float_t>(lhs.m_value.number_unsigned) == rhs.m_value.number_float;
+        }
+        else if (lhs_type == value_t::number_float and rhs_type == value_t::number_unsigned)
+        {
+            return lhs.m_value.number_float == static_cast<number_float_t>(rhs.m_value.number_unsigned);
+        }
+        else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_integer)
+        {
+            return static_cast<number_integer_t>(lhs.m_value.number_unsigned) == rhs.m_value.number_integer;
+        }
+        else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_unsigned)
+        {
+            return lhs.m_value.number_integer == static_cast<number_integer_t>(rhs.m_value.number_unsigned);
+        }
+
+        return false;
+    }
+
+    /*!
+    @brief comparison: equal
+
+    The functions compares the given JSON value against a null pointer. As the
+    null pointer can be used to initialize a JSON value to null, a comparison
+    of JSON value @a v with a null pointer should be equivalent to call
+    `v.is_null()`.
+
+    @param[in] v  JSON value to consider
+    @return whether @a v is null
+
+    @complexity Constant.
+
+    @liveexample{The example compares several JSON types to the null pointer.
+    ,operator__equal__nullptr_t}
+
+    @since version 1.0.0
+    */
+    friend bool operator==(const_reference v, std::nullptr_t) noexcept
+    {
+        return v.is_null();
+    }
+
+    /*!
+    @brief comparison: equal
+    @copydoc operator==(const_reference, std::nullptr_t)
+    */
+    friend bool operator==(std::nullptr_t, const_reference v) noexcept
+    {
+        return v.is_null();
+    }
+
+    /*!
+    @brief comparison: not equal
+
+    Compares two JSON values for inequality by calculating `not (lhs == rhs)`.
+
+    @param[in] lhs  first JSON value to consider
+    @param[in] rhs  second JSON value to consider
+    @return whether the values @a lhs and @a rhs are not equal
+
+    @complexity Linear.
+
+    @liveexample{The example demonstrates comparing several JSON
+    types.,operator__notequal}
+
+    @since version 1.0.0
+    */
+    friend bool operator!=(const_reference lhs, const_reference rhs) noexcept
+    {
+        return not (lhs == rhs);
+    }
+
+    /*!
+    @brief comparison: not equal
+
+    The functions compares the given JSON value against a null pointer. As the
+    null pointer can be used to initialize a JSON value to null, a comparison
+    of JSON value @a v with a null pointer should be equivalent to call
+    `not v.is_null()`.
+
+    @param[in] v  JSON value to consider
+    @return whether @a v is not null
+
+    @complexity Constant.
+
+    @liveexample{The example compares several JSON types to the null pointer.
+    ,operator__notequal__nullptr_t}
+
+    @since version 1.0.0
+    */
+    friend bool operator!=(const_reference v, std::nullptr_t) noexcept
+    {
+        return not v.is_null();
+    }
+
+    /*!
+    @brief comparison: not equal
+    @copydoc operator!=(const_reference, std::nullptr_t)
+    */
+    friend bool operator!=(std::nullptr_t, const_reference v) noexcept
+    {
+        return not v.is_null();
+    }
+
+    /*!
+    @brief comparison: less than
+
+    Compares whether one JSON value @a lhs is less than another JSON value @a
+    rhs according to the following rules:
+    - If @a lhs and @a rhs have the same type, the values are compared using
+      the default `<` operator.
+    - Integer and floating-point numbers are automatically converted before
+      comparison
+    - In case @a lhs and @a rhs have different types, the values are ignored
+      and the order of the types is considered, see
+      @ref operator<(const value_t, const value_t).
+
+    @param[in] lhs  first JSON value to consider
+    @param[in] rhs  second JSON value to consider
+    @return whether @a lhs is less than @a rhs
+
+    @complexity Linear.
+
+    @liveexample{The example demonstrates comparing several JSON
+    types.,operator__less}
+
+    @since version 1.0.0
+    */
+    friend bool operator<(const_reference lhs, const_reference rhs) noexcept
+    {
+        const auto lhs_type = lhs.type();
+        const auto rhs_type = rhs.type();
+
+        if (lhs_type == rhs_type)
+        {
+            switch (lhs_type)
+            {
+                case value_t::array:
+                {
+                    return *lhs.m_value.array < *rhs.m_value.array;
+                }
+                case value_t::object:
+                {
+                    return *lhs.m_value.object < *rhs.m_value.object;
+                }
+                case value_t::null:
+                {
+                    return false;
+                }
+                case value_t::string:
+                {
+                    return *lhs.m_value.string < *rhs.m_value.string;
+                }
+                case value_t::boolean:
+                {
+                    return lhs.m_value.boolean < rhs.m_value.boolean;
+                }
+                case value_t::number_integer:
+                {
+                    return lhs.m_value.number_integer < rhs.m_value.number_integer;
+                }
+                case value_t::number_unsigned:
+                {
+                    return lhs.m_value.number_unsigned < rhs.m_value.number_unsigned;
+                }
+                case value_t::number_float:
+                {
+                    return lhs.m_value.number_float < rhs.m_value.number_float;
+                }
+                default:
+                {
+                    return false;
+                }
+            }
+        }
+        else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
+        {
+            return static_cast<number_float_t>(lhs.m_value.number_integer) < rhs.m_value.number_float;
+        }
+        else if (lhs_type == value_t::number_float and rhs_type == value_t::number_integer)
+        {
+            return lhs.m_value.number_float < static_cast<number_float_t>(rhs.m_value.number_integer);
+        }
+        else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_float)
+        {
+            return static_cast<number_float_t>(lhs.m_value.number_unsigned) < rhs.m_value.number_float;
+        }
+        else if (lhs_type == value_t::number_float and rhs_type == value_t::number_unsigned)
+        {
+            return lhs.m_value.number_float < static_cast<number_float_t>(rhs.m_value.number_unsigned);
+        }
+        else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_unsigned)
+        {
+            return lhs.m_value.number_integer < static_cast<number_integer_t>(rhs.m_value.number_unsigned);
+        }
+        else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_integer)
+        {
+            return static_cast<number_integer_t>(lhs.m_value.number_unsigned) < rhs.m_value.number_integer;
+        }
+
+        // We only reach this line if we cannot compare values. In that case,
+        // we compare types. Note we have to call the operator explicitly,
+        // because MSVC has problems otherwise.
+        return operator<(lhs_type, rhs_type);
+    }
+
+    /*!
+    @brief comparison: less than or equal
+
+    Compares whether one JSON value @a lhs is less than or equal to another
+    JSON value by calculating `not (rhs < lhs)`.
+
+    @param[in] lhs  first JSON value to consider
+    @param[in] rhs  second JSON value to consider
+    @return whether @a lhs is less than or equal to @a rhs
+
+    @complexity Linear.
+
+    @liveexample{The example demonstrates comparing several JSON
+    types.,operator__greater}
+
+    @since version 1.0.0
+    */
+    friend bool operator<=(const_reference lhs, const_reference rhs) noexcept
+    {
+        return not (rhs < lhs);
+    }
+
+    /*!
+    @brief comparison: greater than
+
+    Compares whether one JSON value @a lhs is greater than another
+    JSON value by calculating `not (lhs <= rhs)`.
+
+    @param[in] lhs  first JSON value to consider
+    @param[in] rhs  second JSON value to consider
+    @return whether @a lhs is greater than to @a rhs
+
+    @complexity Linear.
+
+    @liveexample{The example demonstrates comparing several JSON
+    types.,operator__lessequal}
+
+    @since version 1.0.0
+    */
+    friend bool operator>(const_reference lhs, const_reference rhs) noexcept
+    {
+        return not (lhs <= rhs);
+    }
+
+    /*!
+    @brief comparison: greater than or equal
+
+    Compares whether one JSON value @a lhs is greater than or equal to another
+    JSON value by calculating `not (lhs < rhs)`.
+
+    @param[in] lhs  first JSON value to consider
+    @param[in] rhs  second JSON value to consider
+    @return whether @a lhs is greater than or equal to @a rhs
+
+    @complexity Linear.
+
+    @liveexample{The example demonstrates comparing several JSON
+    types.,operator__greaterequal}
+
+    @since version 1.0.0
+    */
+    friend bool operator>=(const_reference lhs, const_reference rhs) noexcept
+    {
+        return not (lhs < rhs);
+    }
+
+    /// @}
+
+
+    ///////////////////
+    // serialization //
+    ///////////////////
+
+    /// @name serialization
+    /// @{
+
+    /*!
+    @brief serialize to stream
+
+    Serialize the given JSON value @a j to the output stream @a o. The JSON
+    value will be serialized using the @ref dump member function. The
+    indentation of the output can be controlled with the member variable
+    `width` of the output stream @a o. For instance, using the manipulator
+    `std::setw(4)` on @a o sets the indentation level to `4` and the
+    serialization result is the same as calling `dump(4)`.
+
+    @note During serializaion, the locale and the precision of the output
+    stream @a o are changed. The original values are restored when the
+    function returns.
+
+    @param[in,out] o  stream to serialize to
+    @param[in] j  JSON value to serialize
+
+    @return the stream @a o
+
+    @complexity Linear.
+
+    @liveexample{The example below shows the serialization with different
+    parameters to `width` to adjust the indentation level.,operator_serialize}
+
+    @since version 1.0.0
+    */
+    friend std::ostream& operator<<(std::ostream& o, const basic_json& j)
+    {
+        // read width member and use it as indentation parameter if nonzero
+        const bool pretty_print = (o.width() > 0);
+        const auto indentation = (pretty_print ? o.width() : 0);
+
+        // reset width to 0 for subsequent calls to this stream
+        o.width(0);
+
+        // fix locale problems
+        const auto old_locale = o.imbue(std::locale(std::locale(), new DecimalSeparator));
+        // set precision
+
+        // 6, 15 or 16 digits of precision allows round-trip IEEE 754
+        // string->float->string, string->double->string or string->long
+        // double->string; to be safe, we read this value from
+        // std::numeric_limits<number_float_t>::digits10
+        const auto old_precision = o.precision(std::numeric_limits<double>::digits10);
+
+        // do the actual serialization
+        j.dump(o, pretty_print, static_cast<unsigned int>(indentation));
+
+        // reset locale and precision
+        o.imbue(old_locale);
+        o.precision(old_precision);
+        return o;
+    }
+
+    /*!
+    @brief serialize to stream
+    @copydoc operator<<(std::ostream&, const basic_json&)
+    */
+    friend std::ostream& operator>>(const basic_json& j, std::ostream& o)
+    {
+        return o << j;
+    }
+
+    /// @}
+
+
+    /////////////////////
+    // deserialization //
+    /////////////////////
+
+    /// @name deserialization
+    /// @{
+
+    /*!
+    @brief deserialize from an array
+
+    This function reads from an array of 1-byte values.
+
+    @pre Each element of the container has a size of 1 byte. Violating this
+    precondition yields undefined behavior. **This precondition is enforced
+    with a static assertion.**
+
+    @param[in] array  array to read from
+    @param[in] cb  a parser callback function of type @ref parser_callback_t
+    which is used to control the deserialization by filtering unwanted values
+    (optional)
+
+    @return result of the deserialization
+
+    @complexity Linear in the length of the input. The parser is a predictive
+    LL(1) parser. The complexity can be higher if the parser callback function
+    @a cb has a super-linear complexity.
+
+    @note A UTF-8 byte order mark is silently ignored.
+
+    @liveexample{The example below demonstrates the `parse()` function reading
+    from an array.,parse__array__parser_callback_t}
+
+    @since version 2.0.3
+    */
+    template<class T, std::size_t N>
+    static basic_json parse(T (&array)[N],
+                            const parser_callback_t cb = nullptr)
+    {
+        // delegate the call to the iterator-range parse overload
+        return parse(std::begin(array), std::end(array), cb);
+    }
+
+    /*!
+    @brief deserialize from string literal
+
+    @tparam CharT character/literal type with size of 1 byte
+    @param[in] s  string literal to read a serialized JSON value from
+    @param[in] cb a parser callback function of type @ref parser_callback_t
+    which is used to control the deserialization by filtering unwanted values
+    (optional)
+
+    @return result of the deserialization
+
+    @complexity Linear in the length of the input. The parser is a predictive
+    LL(1) parser. The complexity can be higher if the parser callback function
+    @a cb has a super-linear complexity.
+
+    @note A UTF-8 byte order mark is silently ignored.
+    @note String containers like `std::string` or @ref string_t can be parsed
+          with @ref parse(const ContiguousContainer&, const parser_callback_t)
+
+    @liveexample{The example below demonstrates the `parse()` function with
+    and without callback function.,parse__string__parser_callback_t}
+
+    @sa @ref parse(std::istream&, const parser_callback_t) for a version that
+    reads from an input stream
+
+    @since version 1.0.0 (originally for @ref string_t)
+    */
+    template<typename CharPT, typename std::enable_if<
+                 std::is_pointer<CharPT>::value and
+                 std::is_integral<typename std::remove_pointer<CharPT>::type>::value and
+                 sizeof(typename std::remove_pointer<CharPT>::type) == 1, int>::type = 0>
+    static basic_json parse(const CharPT s,
+                            const parser_callback_t cb = nullptr)
+    {
+        return parser(reinterpret_cast<const char*>(s), cb).parse();
+    }
+
+    /*!
+    @brief deserialize from stream
+
+    @param[in,out] i  stream to read a serialized JSON value from
+    @param[in] cb a parser callback function of type @ref parser_callback_t
+    which is used to control the deserialization by filtering unwanted values
+    (optional)
+
+    @return result of the deserialization
+
+    @complexity Linear in the length of the input. The parser is a predictive
+    LL(1) parser. The complexity can be higher if the parser callback function
+    @a cb has a super-linear complexity.
+
+    @note A UTF-8 byte order mark is silently ignored.
+
+    @liveexample{The example below demonstrates the `parse()` function with
+    and without callback function.,parse__istream__parser_callback_t}
+
+    @sa @ref parse(const char*, const parser_callback_t) for a version
+    that reads from a string
+
+    @since version 1.0.0
+    */
+    static basic_json parse(std::istream& i,
+                            const parser_callback_t cb = nullptr)
+    {
+        return parser(i, cb).parse();
+    }
+
+    /*!
+    @copydoc parse(std::istream&, const parser_callback_t)
+    */
+    static basic_json parse(std::istream&& i,
+                            const parser_callback_t cb = nullptr)
+    {
+        return parser(i, cb).parse();
+    }
+
+    /*!
+    @brief deserialize from an iterator range with contiguous storage
+
+    This function reads from an iterator range of a container with contiguous
+    storage of 1-byte values. Compatible container types include
+    `std::vector`, `std::string`, `std::array`, `std::valarray`, and
+    `std::initializer_list`. Furthermore, C-style arrays can be used with
+    `std::begin()`/`std::end()`. User-defined containers can be used as long
+    as they implement random-access iterators and a contiguous storage.
+
+    @pre The iterator range is contiguous. Violating this precondition yields
+    undefined behavior. **This precondition is enforced with an assertion.**
+    @pre Each element in the range has a size of 1 byte. Violating this
+    precondition yields undefined behavior. **This precondition is enforced
+    with a static assertion.**
+
+    @warning There is no way to enforce all preconditions at compile-time. If
+             the function is called with noncompliant iterators and with
+             assertions switched off, the behavior is undefined and will most
+             likely yield segmentation violation.
+
+    @tparam IteratorType iterator of container with contiguous storage
+    @param[in] first  begin of the range to parse (included)
+    @param[in] last  end of the range to parse (excluded)
+    @param[in] cb  a parser callback function of type @ref parser_callback_t
+    which is used to control the deserialization by filtering unwanted values
+    (optional)
+
+    @return result of the deserialization
+
+    @complexity Linear in the length of the input. The parser is a predictive
+    LL(1) parser. The complexity can be higher if the parser callback function
+    @a cb has a super-linear complexity.
+
+    @note A UTF-8 byte order mark is silently ignored.
+
+    @liveexample{The example below demonstrates the `parse()` function reading
+    from an iterator range.,parse__iteratortype__parser_callback_t}
+
+    @since version 2.0.3
+    */
+    template<class IteratorType, typename std::enable_if<
+                 std::is_base_of<
+                     std::random_access_iterator_tag,
+                     typename std::iterator_traits<IteratorType>::iterator_category>::value, int>::type = 0>
+    static basic_json parse(IteratorType first, IteratorType last,
+                            const parser_callback_t cb = nullptr)
+    {
+        // assertion to check that the iterator range is indeed contiguous,
+        // see http://stackoverflow.com/a/35008842/266378 for more discussion
+        assert(std::accumulate(first, last, std::make_pair<bool, int>(true, 0),
+                               [&first](std::pair<bool, int> res, decltype(*first) val)
+        {
+            res.first &= (val == *(std::next(std::addressof(*first), res.second++)));
+            return res;
+        }).first);
+
+        // assertion to check that each element is 1 byte long
+        static_assert(sizeof(typename std::iterator_traits<IteratorType>::value_type) == 1,
+                      "each element in the iterator range must have the size of 1 byte");
+
+        // if iterator range is empty, create a parser with an empty string
+        // to generate "unexpected EOF" error message
+        if (std::distance(first, last) <= 0)
+        {
+            return parser("").parse();
+        }
+
+        return parser(first, last, cb).parse();
+    }
+
+    /*!
+    @brief deserialize from a container with contiguous storage
+
+    This function reads from a container with contiguous storage of 1-byte
+    values. Compatible container types include `std::vector`, `std::string`,
+    `std::array`, and `std::initializer_list`. User-defined containers can be
+    used as long as they implement random-access iterators and a contiguous
+    storage.
+
+    @pre The container storage is contiguous. Violating this precondition
+    yields undefined behavior. **This precondition is enforced with an
+    assertion.**
+    @pre Each element of the container has a size of 1 byte. Violating this
+    precondition yields undefined behavior. **This precondition is enforced
+    with a static assertion.**
+
+    @warning There is no way to enforce all preconditions at compile-time. If
+             the function is called with a noncompliant container and with
+             assertions switched off, the behavior is undefined and will most
+             likely yield segmentation violation.
+
+    @tparam ContiguousContainer container type with contiguous storage
+    @param[in] c  container to read from
+    @param[in] cb  a parser callback function of type @ref parser_callback_t
+    which is used to control the deserialization by filtering unwanted values
+    (optional)
+
+    @return result of the deserialization
+
+    @complexity Linear in the length of the input. The parser is a predictive
+    LL(1) parser. The complexity can be higher if the parser callback function
+    @a cb has a super-linear complexity.
+
+    @note A UTF-8 byte order mark is silently ignored.
+
+    @liveexample{The example below demonstrates the `parse()` function reading
+    from a contiguous container.,parse__contiguouscontainer__parser_callback_t}
+
+    @since version 2.0.3
+    */
+    template<class ContiguousContainer, typename std::enable_if<
+                 not std::is_pointer<ContiguousContainer>::value and
+                 std::is_base_of<
+                     std::random_access_iterator_tag,
+                     typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value
+                 , int>::type = 0>
+    static basic_json parse(const ContiguousContainer& c,
+                            const parser_callback_t cb = nullptr)
+    {
+        // delegate the call to the iterator-range parse overload
+        return parse(std::begin(c), std::end(c), cb);
+    }
+
+    /*!
+    @brief deserialize from stream
+
+    Deserializes an input stream to a JSON value.
+
+    @param[in,out] i  input stream to read a serialized JSON value from
+    @param[in,out] j  JSON value to write the deserialized input to
+
+    @throw std::invalid_argument in case of parse errors
+
+    @complexity Linear in the length of the input. The parser is a predictive
+    LL(1) parser.
+
+    @note A UTF-8 byte order mark is silently ignored.
+
+    @liveexample{The example below shows how a JSON value is constructed by
+    reading a serialization from a stream.,operator_deserialize}
+
+    @sa parse(std::istream&, const parser_callback_t) for a variant with a
+    parser callback function to filter values while parsing
+
+    @since version 1.0.0
+    */
+    friend std::istream& operator<<(basic_json& j, std::istream& i)
+    {
+        j = parser(i).parse();
+        return i;
+    }
+
+    /*!
+    @brief deserialize from stream
+    @copydoc operator<<(basic_json&, std::istream&)
+    */
+    friend std::istream& operator>>(std::istream& i, basic_json& j)
+    {
+        j = parser(i).parse();
+        return i;
+    }
+
+    /// @}
+
+
+  private:
+    ///////////////////////////
+    // convenience functions //
+    ///////////////////////////
+
+    /*!
+    @brief return the type as string
+
+    Returns the type name as string to be used in error messages - usually to
+    indicate that a function was called on a wrong JSON type.
+
+    @return basically a string representation of a the @a m_type member
+
+    @complexity Constant.
+
+    @since version 1.0.0
+    */
+    std::string type_name() const
+    {
+        switch (m_type)
+        {
+            case value_t::null:
+                return "null";
+            case value_t::object:
+                return "object";
+            case value_t::array:
+                return "array";
+            case value_t::string:
+                return "string";
+            case value_t::boolean:
+                return "boolean";
+            case value_t::discarded:
+                return "discarded";
+            default:
+                return "number";
+        }
+    }
+
+    /*!
+    @brief calculates the extra space to escape a JSON string
+
+    @param[in] s  the string to escape
+    @return the number of characters required to escape string @a s
+
+    @complexity Linear in the length of string @a s.
+    */
+    static std::size_t extra_space(const string_t& s) noexcept
+    {
+        return std::accumulate(s.begin(), s.end(), size_t{},
+                               [](size_t res, typename string_t::value_type c)
+        {
+            switch (c)
+            {
+                case '"':
+                case '\\':
+                case '\b':
+                case '\f':
+                case '\n':
+                case '\r':
+                case '\t':
+                {
+                    // from c (1 byte) to \x (2 bytes)
+                    return res + 1;
+                }
+
+                default:
+                {
+                    if (c >= 0x00 and c <= 0x1f)
+                    {
+                        // from c (1 byte) to \uxxxx (6 bytes)
+                        return res + 5;
+                    }
+                    else
+                    {
+                        return res;
+                    }
+                }
+            }
+        });
+    }
+
+    /*!
+    @brief escape a string
+
+    Escape a string by replacing certain special characters by a sequence of
+    an escape character (backslash) and another character and other control
+    characters by a sequence of "\u" followed by a four-digit hex
+    representation.
+
+    @param[in] s  the string to escape
+    @return  the escaped string
+
+    @complexity Linear in the length of string @a s.
+    */
+    static string_t escape_string(const string_t& s)
+    {
+        const auto space = extra_space(s);
+        if (space == 0)
+        {
+            return s;
+        }
+
+        // create a result string of necessary size
+        string_t result(s.size() + space, '\\');
+        std::size_t pos = 0;
+
+        for (const auto& c : s)
+        {
+            switch (c)
+            {
+                // quotation mark (0x22)
+                case '"':
+                {
+                    result[pos + 1] = '"';
+                    pos += 2;
+                    break;
+                }
+
+                // reverse solidus (0x5c)
+                case '\\':
+                {
+                    // nothing to change
+                    pos += 2;
+                    break;
+                }
+
+                // backspace (0x08)
+                case '\b':
+                {
+                    result[pos + 1] = 'b';
+                    pos += 2;
+                    break;
+                }
+
+                // formfeed (0x0c)
+                case '\f':
+                {
+                    result[pos + 1] = 'f';
+                    pos += 2;
+                    break;
+                }
+
+                // newline (0x0a)
+                case '\n':
+                {
+                    result[pos + 1] = 'n';
+                    pos += 2;
+                    break;
+                }
+
+                // carriage return (0x0d)
+                case '\r':
+                {
+                    result[pos + 1] = 'r';
+                    pos += 2;
+                    break;
+                }
+
+                // horizontal tab (0x09)
+                case '\t':
+                {
+                    result[pos + 1] = 't';
+                    pos += 2;
+                    break;
+                }
+
+                default:
+                {
+                    if (c >= 0x00 and c <= 0x1f)
+                    {
+                        // convert a number 0..15 to its hex representation
+                        // (0..f)
+                        static const char hexify[16] =
+                        {
+                            '0', '1', '2', '3', '4', '5', '6', '7',
+                            '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+                        };
+
+                        // print character c as \uxxxx
+                        for (const char m :
+                    { 'u', '0', '0', hexify[c >> 4], hexify[c & 0x0f]
+                        })
+                        {
+                            result[++pos] = m;
+                        }
+
+                        ++pos;
+                    }
+                    else
+                    {
+                        // all other characters are added as-is
+                        result[pos++] = c;
+                    }
+                    break;
+                }
+            }
+        }
+
+        return result;
+    }
+
+    /*!
+    @brief internal implementation of the serialization function
+
+    This function is called by the public member function dump and organizes
+    the serialization internally. The indentation level is propagated as
+    additional parameter. In case of arrays and objects, the function is
+    called recursively. Note that
+
+    - strings and object keys are escaped using `escape_string()`
+    - integer numbers are converted implicitly via `operator<<`
+    - floating-point numbers are converted to a string using `"%g"` format
+
+    @param[out] o              stream to write to
+    @param[in] pretty_print    whether the output shall be pretty-printed
+    @param[in] indent_step     the indent level
+    @param[in] current_indent  the current indent level (only used internally)
+    */
+    void dump(std::ostream& o,
+              const bool pretty_print,
+              const unsigned int indent_step,
+              const unsigned int current_indent = 0) const
+    {
+        // variable to hold indentation for recursive calls
+        unsigned int new_indent = current_indent;
+
+        switch (m_type)
+        {
+            case value_t::object:
+            {
+                if (m_value.object->empty())
+                {
+                    o << "{}";
+                    return;
+                }
+
+                o << "{";
+
+                // increase indentation
+                if (pretty_print)
+                {
+                    new_indent += indent_step;
+                    o << "\n";
+                }
+
+                for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i)
+                {
+                    if (i != m_value.object->cbegin())
+                    {
+                        o << (pretty_print ? ",\n" : ",");
+                    }
+                    o << string_t(new_indent, ' ') << "\""
+                      << escape_string(i->first) << "\":"
+                      << (pretty_print ? " " : "");
+                    i->second.dump(o, pretty_print, indent_step, new_indent);
+                }
+
+                // decrease indentation
+                if (pretty_print)
+                {
+                    new_indent -= indent_step;
+                    o << "\n";
+                }
+
+                o << string_t(new_indent, ' ') + "}";
+                return;
+            }
+
+            case value_t::array:
+            {
+                if (m_value.array->empty())
+                {
+                    o << "[]";
+                    return;
+                }
+
+                o << "[";
+
+                // increase indentation
+                if (pretty_print)
+                {
+                    new_indent += indent_step;
+                    o << "\n";
+                }
+
+                for (auto i = m_value.array->cbegin(); i != m_value.array->cend(); ++i)
+                {
+                    if (i != m_value.array->cbegin())
+                    {
+                        o << (pretty_print ? ",\n" : ",");
+                    }
+                    o << string_t(new_indent, ' ');
+                    i->dump(o, pretty_print, indent_step, new_indent);
+                }
+
+                // decrease indentation
+                if (pretty_print)
+                {
+                    new_indent -= indent_step;
+                    o << "\n";
+                }
+
+                o << string_t(new_indent, ' ') << "]";
+                return;
+            }
+
+            case value_t::string:
+            {
+                o << string_t("\"") << escape_string(*m_value.string) << "\"";
+                return;
+            }
+
+            case value_t::boolean:
+            {
+                o << (m_value.boolean ? "true" : "false");
+                return;
+            }
+
+            case value_t::number_integer:
+            {
+                o << m_value.number_integer;
+                return;
+            }
+
+            case value_t::number_unsigned:
+            {
+                o << m_value.number_unsigned;
+                return;
+            }
+
+            case value_t::number_float:
+            {
+                if (m_value.number_float == 0)
+                {
+                    // special case for zero to get "0.0"/"-0.0"
+                    o << (std::signbit(m_value.number_float) ? "-0.0" : "0.0");
+                }
+                else
+                {
+                    o << m_value.number_float;
+                }
+                return;
+            }
+
+            case value_t::discarded:
+            {
+                o << "<discarded>";
+                return;
+            }
+
+            case value_t::null:
+            {
+                o << "null";
+                return;
+            }
+        }
+    }
+
+  private:
+    //////////////////////
+    // member variables //
+    //////////////////////
+
+    /// the type of the current element
+    value_t m_type = value_t::null;
+
+    /// the value of the current element
+    json_value m_value = {};
+
+
+  private:
+    ///////////////
+    // iterators //
+    ///////////////
+
+    /*!
+    @brief an iterator for primitive JSON types
+
+    This class models an iterator for primitive JSON types (boolean, number,
+    string). It's only purpose is to allow the iterator/const_iterator classes
+    to "iterate" over primitive values. Internally, the iterator is modeled by
+    a `difference_type` variable. Value begin_value (`0`) models the begin,
+    end_value (`1`) models past the end.
+    */
+    class primitive_iterator_t
+    {
+      public:
+        /// set iterator to a defined beginning
+        void set_begin() noexcept
+        {
+            m_it = begin_value;
+        }
+
+        /// set iterator to a defined past the end
+        void set_end() noexcept
+        {
+            m_it = end_value;
+        }
+
+        /// return whether the iterator can be dereferenced
+        constexpr bool is_begin() const noexcept
+        {
+            return (m_it == begin_value);
+        }
+
+        /// return whether the iterator is at end
+        constexpr bool is_end() const noexcept
+        {
+            return (m_it == end_value);
+        }
+
+        /// return reference to the value to change and compare
+        operator difference_type& () noexcept
+        {
+            return m_it;
+        }
+
+        /// return value to compare
+        constexpr operator difference_type () const noexcept
+        {
+            return m_it;
+        }
+
+      private:
+        static constexpr difference_type begin_value = 0;
+        static constexpr difference_type end_value = begin_value + 1;
+
+        /// iterator as signed integer type
+        difference_type m_it = std::numeric_limits<std::ptrdiff_t>::denorm_min();
+    };
+
+    /*!
+    @brief an iterator value
+
+    @note This structure could easily be a union, but MSVC currently does not
+    allow unions members with complex constructors, see
+    https://github.com/nlohmann/json/pull/105.
+    */
+    struct internal_iterator
+    {
+        /// iterator for JSON objects
+        typename object_t::iterator object_iterator;
+        /// iterator for JSON arrays
+        typename array_t::iterator array_iterator;
+        /// generic iterator for all other types
+        primitive_iterator_t primitive_iterator;
+
+        /// create an uninitialized internal_iterator
+        internal_iterator() noexcept
+            : object_iterator(), array_iterator(), primitive_iterator()
+        {}
+    };
+
+    /// proxy class for the iterator_wrapper functions
+    template<typename IteratorType>
+    class iteration_proxy
+    {
+      private:
+        /// helper class for iteration
+        class iteration_proxy_internal
+        {
+          private:
+            /// the iterator
+            IteratorType anchor;
+            /// an index for arrays (used to create key names)
+            size_t array_index = 0;
+
+          public:
+            explicit iteration_proxy_internal(IteratorType it) noexcept
+                : anchor(it)
+            {}
+
+            /// dereference operator (needed for range-based for)
+            iteration_proxy_internal& operator*()
+            {
+                return *this;
+            }
+
+            /// increment operator (needed for range-based for)
+            iteration_proxy_internal& operator++()
+            {
+                ++anchor;
+                ++array_index;
+
+                return *this;
+            }
+
+            /// inequality operator (needed for range-based for)
+            bool operator!= (const iteration_proxy_internal& o) const
+            {
+                return anchor != o.anchor;
+            }
+
+            /// return key of the iterator
+            typename basic_json::string_t key() const
+            {
+                assert(anchor.m_object != nullptr);
+
+                switch (anchor.m_object->type())
+                {
+                    // use integer array index as key
+                    case value_t::array:
+                    {
+                        return std::to_string(array_index);
+                    }
+
+                    // use key from the object
+                    case value_t::object:
+                    {
+                        return anchor.key();
+                    }
+
+                    // use an empty key for all primitive types
+                    default:
+                    {
+                        return "";
+                    }
+                }
+            }
+
+            /// return value of the iterator
+            typename IteratorType::reference value() const
+            {
+                return anchor.value();
+            }
+        };
+
+        /// the container to iterate
+        typename IteratorType::reference container;
+
+      public:
+        /// construct iteration proxy from a container
+        explicit iteration_proxy(typename IteratorType::reference cont)
+            : container(cont)
+        {}
+
+        /// return iterator begin (needed for range-based for)
+        iteration_proxy_internal begin() noexcept
+        {
+            return iteration_proxy_internal(container.begin());
+        }
+
+        /// return iterator end (needed for range-based for)
+        iteration_proxy_internal end() noexcept
+        {
+            return iteration_proxy_internal(container.end());
+        }
+    };
+
+  public:
+    /*!
+    @brief a const random access iterator for the @ref basic_json class
+
+    This class implements a const iterator for the @ref basic_json class. From
+    this class, the @ref iterator class is derived.
+
+    @note An iterator is called *initialized* when a pointer to a JSON value
+          has been set (e.g., by a constructor or a copy assignment). If the
+          iterator is default-constructed, it is *uninitialized* and most
+          methods are undefined. **The library uses assertions to detect calls
+          on uninitialized iterators.**
+
+    @requirement The class satisfies the following concept requirements:
+    - [RandomAccessIterator](http://en.cppreference.com/w/cpp/concept/RandomAccessIterator):
+      The iterator that can be moved to point (forward and backward) to any
+      element in constant time.
+
+    @since version 1.0.0
+    */
+    class const_iterator : public std::iterator<std::random_access_iterator_tag, const basic_json>
+    {
+        /// allow basic_json to access private members
+        friend class basic_json;
+
+      public:
+        /// the type of the values when the iterator is dereferenced
+        using value_type = typename basic_json::value_type;
+        /// a type to represent differences between iterators
+        using difference_type = typename basic_json::difference_type;
+        /// defines a pointer to the type iterated over (value_type)
+        using pointer = typename basic_json::const_pointer;
+        /// defines a reference to the type iterated over (value_type)
+        using reference = typename basic_json::const_reference;
+        /// the category of the iterator
+        using iterator_category = std::bidirectional_iterator_tag;
+
+        /// default constructor
+        const_iterator() = default;
+
+        /*!
+        @brief constructor for a given JSON instance
+        @param[in] object  pointer to a JSON object for this iterator
+        @pre object != nullptr
+        @post The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        explicit const_iterator(pointer object) noexcept
+            : m_object(object)
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    m_it.object_iterator = typename object_t::iterator();
+                    break;
+                }
+
+                case basic_json::value_t::array:
+                {
+                    m_it.array_iterator = typename array_t::iterator();
+                    break;
+                }
+
+                default:
+                {
+                    m_it.primitive_iterator = primitive_iterator_t();
+                    break;
+                }
+            }
+        }
+
+        /*!
+        @brief copy constructor given a non-const iterator
+        @param[in] other  iterator to copy from
+        @note It is not checked whether @a other is initialized.
+        */
+        explicit const_iterator(const iterator& other) noexcept
+            : m_object(other.m_object)
+        {
+            if (m_object != nullptr)
+            {
+                switch (m_object->m_type)
+                {
+                    case basic_json::value_t::object:
+                    {
+                        m_it.object_iterator = other.m_it.object_iterator;
+                        break;
+                    }
+
+                    case basic_json::value_t::array:
+                    {
+                        m_it.array_iterator = other.m_it.array_iterator;
+                        break;
+                    }
+
+                    default:
+                    {
+                        m_it.primitive_iterator = other.m_it.primitive_iterator;
+                        break;
+                    }
+                }
+            }
+        }
+
+        /*!
+        @brief copy constructor
+        @param[in] other  iterator to copy from
+        @note It is not checked whether @a other is initialized.
+        */
+        const_iterator(const const_iterator& other) noexcept
+            : m_object(other.m_object), m_it(other.m_it)
+        {}
+
+        /*!
+        @brief copy assignment
+        @param[in,out] other  iterator to copy from
+        @note It is not checked whether @a other is initialized.
+        */
+        const_iterator& operator=(const_iterator other) noexcept(
+            std::is_nothrow_move_constructible<pointer>::value and
+            std::is_nothrow_move_assignable<pointer>::value and
+            std::is_nothrow_move_constructible<internal_iterator>::value and
+            std::is_nothrow_move_assignable<internal_iterator>::value
+        )
+        {
+            std::swap(m_object, other.m_object);
+            std::swap(m_it, other.m_it);
+            return *this;
+        }
+
+      private:
+        /*!
+        @brief set the iterator to the first value
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        void set_begin() noexcept
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    m_it.object_iterator = m_object->m_value.object->begin();
+                    break;
+                }
+
+                case basic_json::value_t::array:
+                {
+                    m_it.array_iterator = m_object->m_value.array->begin();
+                    break;
+                }
+
+                case basic_json::value_t::null:
+                {
+                    // set to end so begin()==end() is true: null is empty
+                    m_it.primitive_iterator.set_end();
+                    break;
+                }
+
+                default:
+                {
+                    m_it.primitive_iterator.set_begin();
+                    break;
+                }
+            }
+        }
+
+        /*!
+        @brief set the iterator past the last value
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        void set_end() noexcept
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    m_it.object_iterator = m_object->m_value.object->end();
+                    break;
+                }
+
+                case basic_json::value_t::array:
+                {
+                    m_it.array_iterator = m_object->m_value.array->end();
+                    break;
+                }
+
+                default:
+                {
+                    m_it.primitive_iterator.set_end();
+                    break;
+                }
+            }
+        }
+
+      public:
+        /*!
+        @brief return a reference to the value pointed to by the iterator
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        reference operator*() const
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    assert(m_it.object_iterator != m_object->m_value.object->end());
+                    return m_it.object_iterator->second;
+                }
+
+                case basic_json::value_t::array:
+                {
+                    assert(m_it.array_iterator != m_object->m_value.array->end());
+                    return *m_it.array_iterator;
+                }
+
+                case basic_json::value_t::null:
+                {
+                    throw std::out_of_range("cannot get value");
+                }
+
+                default:
+                {
+                    if (m_it.primitive_iterator.is_begin())
+                    {
+                        return *m_object;
+                    }
+                    else
+                    {
+                        throw std::out_of_range("cannot get value");
+                    }
+                }
+            }
+        }
+
+        /*!
+        @brief dereference the iterator
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        pointer operator->() const
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    assert(m_it.object_iterator != m_object->m_value.object->end());
+                    return &(m_it.object_iterator->second);
+                }
+
+                case basic_json::value_t::array:
+                {
+                    assert(m_it.array_iterator != m_object->m_value.array->end());
+                    return &*m_it.array_iterator;
+                }
+
+                default:
+                {
+                    if (m_it.primitive_iterator.is_begin())
+                    {
+                        return m_object;
+                    }
+                    else
+                    {
+                        throw std::out_of_range("cannot get value");
+                    }
+                }
+            }
+        }
+
+        /*!
+        @brief post-increment (it++)
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        const_iterator operator++(int)
+        {
+            auto result = *this;
+            ++(*this);
+            return result;
+        }
+
+        /*!
+        @brief pre-increment (++it)
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        const_iterator& operator++()
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    std::advance(m_it.object_iterator, 1);
+                    break;
+                }
+
+                case basic_json::value_t::array:
+                {
+                    std::advance(m_it.array_iterator, 1);
+                    break;
+                }
+
+                default:
+                {
+                    ++m_it.primitive_iterator;
+                    break;
+                }
+            }
+
+            return *this;
+        }
+
+        /*!
+        @brief post-decrement (it--)
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        const_iterator operator--(int)
+        {
+            auto result = *this;
+            --(*this);
+            return result;
+        }
+
+        /*!
+        @brief pre-decrement (--it)
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        const_iterator& operator--()
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    std::advance(m_it.object_iterator, -1);
+                    break;
+                }
+
+                case basic_json::value_t::array:
+                {
+                    std::advance(m_it.array_iterator, -1);
+                    break;
+                }
+
+                default:
+                {
+                    --m_it.primitive_iterator;
+                    break;
+                }
+            }
+
+            return *this;
+        }
+
+        /*!
+        @brief  comparison: equal
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        bool operator==(const const_iterator& other) const
+        {
+            // if objects are not the same, the comparison is undefined
+            if (m_object != other.m_object)
+            {
+                throw std::domain_error("cannot compare iterators of different containers");
+            }
+
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    return (m_it.object_iterator == other.m_it.object_iterator);
+                }
+
+                case basic_json::value_t::array:
+                {
+                    return (m_it.array_iterator == other.m_it.array_iterator);
+                }
+
+                default:
+                {
+                    return (m_it.primitive_iterator == other.m_it.primitive_iterator);
+                }
+            }
+        }
+
+        /*!
+        @brief  comparison: not equal
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        bool operator!=(const const_iterator& other) const
+        {
+            return not operator==(other);
+        }
+
+        /*!
+        @brief  comparison: smaller
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        bool operator<(const const_iterator& other) const
+        {
+            // if objects are not the same, the comparison is undefined
+            if (m_object != other.m_object)
+            {
+                throw std::domain_error("cannot compare iterators of different containers");
+            }
+
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    throw std::domain_error("cannot compare order of object iterators");
+                }
+
+                case basic_json::value_t::array:
+                {
+                    return (m_it.array_iterator < other.m_it.array_iterator);
+                }
+
+                default:
+                {
+                    return (m_it.primitive_iterator < other.m_it.primitive_iterator);
+                }
+            }
+        }
+
+        /*!
+        @brief  comparison: less than or equal
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        bool operator<=(const const_iterator& other) const
+        {
+            return not other.operator < (*this);
+        }
+
+        /*!
+        @brief  comparison: greater than
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        bool operator>(const const_iterator& other) const
+        {
+            return not operator<=(other);
+        }
+
+        /*!
+        @brief  comparison: greater than or equal
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        bool operator>=(const const_iterator& other) const
+        {
+            return not operator<(other);
+        }
+
+        /*!
+        @brief  add to iterator
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        const_iterator& operator+=(difference_type i)
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    throw std::domain_error("cannot use offsets with object iterators");
+                }
+
+                case basic_json::value_t::array:
+                {
+                    std::advance(m_it.array_iterator, i);
+                    break;
+                }
+
+                default:
+                {
+                    m_it.primitive_iterator += i;
+                    break;
+                }
+            }
+
+            return *this;
+        }
+
+        /*!
+        @brief  subtract from iterator
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        const_iterator& operator-=(difference_type i)
+        {
+            return operator+=(-i);
+        }
+
+        /*!
+        @brief  add to iterator
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        const_iterator operator+(difference_type i)
+        {
+            auto result = *this;
+            result += i;
+            return result;
+        }
+
+        /*!
+        @brief  subtract from iterator
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        const_iterator operator-(difference_type i)
+        {
+            auto result = *this;
+            result -= i;
+            return result;
+        }
+
+        /*!
+        @brief  return difference
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        difference_type operator-(const const_iterator& other) const
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    throw std::domain_error("cannot use offsets with object iterators");
+                }
+
+                case basic_json::value_t::array:
+                {
+                    return m_it.array_iterator - other.m_it.array_iterator;
+                }
+
+                default:
+                {
+                    return m_it.primitive_iterator - other.m_it.primitive_iterator;
+                }
+            }
+        }
+
+        /*!
+        @brief  access to successor
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        reference operator[](difference_type n) const
+        {
+            assert(m_object != nullptr);
+
+            switch (m_object->m_type)
+            {
+                case basic_json::value_t::object:
+                {
+                    throw std::domain_error("cannot use operator[] for object iterators");
+                }
+
+                case basic_json::value_t::array:
+                {
+                    return *std::next(m_it.array_iterator, n);
+                }
+
+                case basic_json::value_t::null:
+                {
+                    throw std::out_of_range("cannot get value");
+                }
+
+                default:
+                {
+                    if (m_it.primitive_iterator == -n)
+                    {
+                        return *m_object;
+                    }
+                    else
+                    {
+                        throw std::out_of_range("cannot get value");
+                    }
+                }
+            }
+        }
+
+        /*!
+        @brief  return the key of an object iterator
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        typename object_t::key_type key() const
+        {
+            assert(m_object != nullptr);
+
+            if (m_object->is_object())
+            {
+                return m_it.object_iterator->first;
+            }
+            else
+            {
+                throw std::domain_error("cannot use key() for non-object iterators");
+            }
+        }
+
+        /*!
+        @brief  return the value of an iterator
+        @pre The iterator is initialized; i.e. `m_object != nullptr`.
+        */
+        reference value() const
+        {
+            return operator*();
+        }
+
+      private:
+        /// associated JSON instance
+        pointer m_object = nullptr;
+        /// the actual iterator of the associated instance
+        internal_iterator m_it = internal_iterator();
+    };
+
+    /*!
+    @brief a mutable random access iterator for the @ref basic_json class
+
+    @requirement The class satisfies the following concept requirements:
+    - [RandomAccessIterator](http://en.cppreference.com/w/cpp/concept/RandomAccessIterator):
+      The iterator that can be moved to point (forward and backward) to any
+      element in constant time.
+    - [OutputIterator](http://en.cppreference.com/w/cpp/concept/OutputIterator):
+      It is possible to write to the pointed-to element.
+
+    @since version 1.0.0
+    */
+    class iterator : public const_iterator
+    {
+      public:
+        using base_iterator = const_iterator;
+        using pointer = typename basic_json::pointer;
+        using reference = typename basic_json::reference;
+
+        /// default constructor
+        iterator() = default;
+
+        /// constructor for a given JSON instance
+        explicit iterator(pointer object) noexcept
+            : base_iterator(object)
+        {}
+
+        /// copy constructor
+        iterator(const iterator& other) noexcept
+            : base_iterator(other)
+        {}
+
+        /// copy assignment
+        iterator& operator=(iterator other) noexcept(
+            std::is_nothrow_move_constructible<pointer>::value and
+            std::is_nothrow_move_assignable<pointer>::value and
+            std::is_nothrow_move_constructible<internal_iterator>::value and
+            std::is_nothrow_move_assignable<internal_iterator>::value
+        )
+        {
+            base_iterator::operator=(other);
+            return *this;
+        }
+
+        /// return a reference to the value pointed to by the iterator
+        reference operator*() const
+        {
+            return const_cast<reference>(base_iterator::operator*());
+        }
+
+        /// dereference the iterator
+        pointer operator->() const
+        {
+            return const_cast<pointer>(base_iterator::operator->());
+        }
+
+        /// post-increment (it++)
+        iterator operator++(int)
+        {
+            iterator result = *this;
+            base_iterator::operator++();
+            return result;
+        }
+
+        /// pre-increment (++it)
+        iterator& operator++()
+        {
+            base_iterator::operator++();
+            return *this;
+        }
+
+        /// post-decrement (it--)
+        iterator operator--(int)
+        {
+            iterator result = *this;
+            base_iterator::operator--();
+            return result;
+        }
+
+        /// pre-decrement (--it)
+        iterator& operator--()
+        {
+            base_iterator::operator--();
+            return *this;
+        }
+
+        /// add to iterator
+        iterator& operator+=(difference_type i)
+        {
+            base_iterator::operator+=(i);
+            return *this;
+        }
+
+        /// subtract from iterator
+        iterator& operator-=(difference_type i)
+        {
+            base_iterator::operator-=(i);
+            return *this;
+        }
+
+        /// add to iterator
+        iterator operator+(difference_type i)
+        {
+            auto result = *this;
+            result += i;
+            return result;
+        }
+
+        /// subtract from iterator
+        iterator operator-(difference_type i)
+        {
+            auto result = *this;
+            result -= i;
+            return result;
+        }
+
+        /// return difference
+        difference_type operator-(const iterator& other) const
+        {
+            return base_iterator::operator-(other);
+        }
+
+        /// access to successor
+        reference operator[](difference_type n) const
+        {
+            return const_cast<reference>(base_iterator::operator[](n));
+        }
+
+        /// return the value of an iterator
+        reference value() const
+        {
+            return const_cast<reference>(base_iterator::value());
+        }
+    };
+
+    /*!
+    @brief a template for a reverse iterator class
+
+    @tparam Base the base iterator type to reverse. Valid types are @ref
+    iterator (to create @ref reverse_iterator) and @ref const_iterator (to
+    create @ref const_reverse_iterator).
+
+    @requirement The class satisfies the following concept requirements:
+    - [RandomAccessIterator](http://en.cppreference.com/w/cpp/concept/RandomAccessIterator):
+      The iterator that can be moved to point (forward and backward) to any
+      element in constant time.
+    - [OutputIterator](http://en.cppreference.com/w/cpp/concept/OutputIterator):
+      It is possible to write to the pointed-to element (only if @a Base is
+      @ref iterator).
+
+    @since version 1.0.0
+    */
+    template<typename Base>
+    class json_reverse_iterator : public std::reverse_iterator<Base>
+    {
+      public:
+        /// shortcut to the reverse iterator adaptor
+        using base_iterator = std::reverse_iterator<Base>;
+        /// the reference type for the pointed-to element
+        using reference = typename Base::reference;
+
+        /// create reverse iterator from iterator
+        json_reverse_iterator(const typename base_iterator::iterator_type& it) noexcept
+            : base_iterator(it)
+        {}
+
+        /// create reverse iterator from base class
+        json_reverse_iterator(const base_iterator& it) noexcept
+            : base_iterator(it)
+        {}
+
+        /// post-increment (it++)
+        json_reverse_iterator operator++(int)
+        {
+            return base_iterator::operator++(1);
+        }
+
+        /// pre-increment (++it)
+        json_reverse_iterator& operator++()
+        {
+            base_iterator::operator++();
+            return *this;
+        }
+
+        /// post-decrement (it--)
+        json_reverse_iterator operator--(int)
+        {
+            return base_iterator::operator--(1);
+        }
+
+        /// pre-decrement (--it)
+        json_reverse_iterator& operator--()
+        {
+            base_iterator::operator--();
+            return *this;
+        }
+
+        /// add to iterator
+        json_reverse_iterator& operator+=(difference_type i)
+        {
+            base_iterator::operator+=(i);
+            return *this;
+        }
+
+        /// add to iterator
+        json_reverse_iterator operator+(difference_type i) const
+        {
+            auto result = *this;
+            result += i;
+            return result;
+        }
+
+        /// subtract from iterator
+        json_reverse_iterator operator-(difference_type i) const
+        {
+            auto result = *this;
+            result -= i;
+            return result;
+        }
+
+        /// return difference
+        difference_type operator-(const json_reverse_iterator& other) const
+        {
+            return this->base() - other.base();
+        }
+
+        /// access to successor
+        reference operator[](difference_type n) const
+        {
+            return *(this->operator+(n));
+        }
+
+        /// return the key of an object iterator
+        typename object_t::key_type key() const
+        {
+            auto it = --this->base();
+            return it.key();
+        }
+
+        /// return the value of an iterator
+        reference value() const
+        {
+            auto it = --this->base();
+            return it.operator * ();
+        }
+    };
+
+
+  private:
+    //////////////////////
+    // lexer and parser //
+    //////////////////////
+
+    /*!
+    @brief lexical analysis
+
+    This class organizes the lexical analysis during JSON deserialization. The
+    core of it is a scanner generated by [re2c](http://re2c.org) that
+    processes a buffer and recognizes tokens according to RFC 7159.
+    */
+    class lexer
+    {
+      public:
+        /// token types for the parser
+        enum class token_type
+        {
+            uninitialized,   ///< indicating the scanner is uninitialized
+            literal_true,    ///< the `true` literal
+            literal_false,   ///< the `false` literal
+            literal_null,    ///< the `null` literal
+            value_string,    ///< a string -- use get_string() for actual value
+            value_number,    ///< a number -- use get_number() for actual value
+            begin_array,     ///< the character for array begin `[`
+            begin_object,    ///< the character for object begin `{`
+            end_array,       ///< the character for array end `]`
+            end_object,      ///< the character for object end `}`
+            name_separator,  ///< the name separator `:`
+            value_separator, ///< the value separator `,`
+            parse_error,     ///< indicating a parse error
+            end_of_input     ///< indicating the end of the input buffer
+        };
+
+        /// the char type to use in the lexer
+        using lexer_char_t = unsigned char;
+
+        /// a lexer from a buffer with given length
+        lexer(const lexer_char_t* buff, const size_t len) noexcept
+            : m_content(buff)
+        {
+            assert(m_content != nullptr);
+            m_start = m_cursor = m_content;
+            m_limit = m_content + len;
+        }
+
+        /// a lexer from an input stream
+        explicit lexer(std::istream& s)
+            : m_stream(&s), m_line_buffer()
+        {
+            // fill buffer
+            fill_line_buffer();
+
+            // skip UTF-8 byte-order mark
+            if (m_line_buffer.size() >= 3 and m_line_buffer.substr(0, 3) == "\xEF\xBB\xBF")
+            {
+                m_line_buffer[0] = ' ';
+                m_line_buffer[1] = ' ';
+                m_line_buffer[2] = ' ';
+            }
+        }
+
+        // switch off unwanted functions (due to pointer members)
+        lexer() = delete;
+        lexer(const lexer&) = delete;
+        lexer operator=(const lexer&) = delete;
+
+        /*!
+        @brief create a string from one or two Unicode code points
+
+        There are two cases: (1) @a codepoint1 is in the Basic Multilingual
+        Plane (U+0000 through U+FFFF) and @a codepoint2 is 0, or (2)
+        @a codepoint1 and @a codepoint2 are a UTF-16 surrogate pair to
+        represent a code point above U+FFFF.
+
+        @param[in] codepoint1  the code point (can be high surrogate)
+        @param[in] codepoint2  the code point (can be low surrogate or 0)
+
+        @return string representation of the code point; the length of the
+        result string is between 1 and 4 characters.
+
+        @throw std::out_of_range if code point is > 0x10ffff; example: `"code
+        points above 0x10FFFF are invalid"`
+        @throw std::invalid_argument if the low surrogate is invalid; example:
+        `""missing or wrong low surrogate""`
+
+        @complexity Constant.
+
+        @see <http://en.wikipedia.org/wiki/UTF-8#Sample_code>
+        */
+        static string_t to_unicode(const std::size_t codepoint1,
+                                   const std::size_t codepoint2 = 0)
+        {
+            // calculate the code point from the given code points
+            std::size_t codepoint = codepoint1;
+
+            // check if codepoint1 is a high surrogate
+            if (codepoint1 >= 0xD800 and codepoint1 <= 0xDBFF)
+            {
+                // check if codepoint2 is a low surrogate
+                if (codepoint2 >= 0xDC00 and codepoint2 <= 0xDFFF)
+                {
+                    codepoint =
+                        // high surrogate occupies the most significant 22 bits
+                        (codepoint1 << 10)
+                        // low surrogate occupies the least significant 15 bits
+                        + codepoint2
+                        // there is still the 0xD800, 0xDC00 and 0x10000 noise
+                        // in the result so we have to subtract with:
+                        // (0xD800 << 10) + DC00 - 0x10000 = 0x35FDC00
+                        - 0x35FDC00;
+                }
+                else
+                {
+                    throw std::invalid_argument("missing or wrong low surrogate");
+                }
+            }
+
+            string_t result;
+
+            if (codepoint < 0x80)
+            {
+                // 1-byte characters: 0xxxxxxx (ASCII)
+                result.append(1, static_cast<typename string_t::value_type>(codepoint));
+            }
+            else if (codepoint <= 0x7ff)
+            {
+                // 2-byte characters: 110xxxxx 10xxxxxx
+                result.append(1, static_cast<typename string_t::value_type>(0xC0 | ((codepoint >> 6) & 0x1F)));
+                result.append(1, static_cast<typename string_t::value_type>(0x80 | (codepoint & 0x3F)));
+            }
+            else if (codepoint <= 0xffff)
+            {
+                // 3-byte characters: 1110xxxx 10xxxxxx 10xxxxxx
+                result.append(1, static_cast<typename string_t::value_type>(0xE0 | ((codepoint >> 12) & 0x0F)));
+                result.append(1, static_cast<typename string_t::value_type>(0x80 | ((codepoint >> 6) & 0x3F)));
+                result.append(1, static_cast<typename string_t::value_type>(0x80 | (codepoint & 0x3F)));
+            }
+            else if (codepoint <= 0x10ffff)
+            {
+                // 4-byte characters: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
+                result.append(1, static_cast<typename string_t::value_type>(0xF0 | ((codepoint >> 18) & 0x07)));
+                result.append(1, static_cast<typename string_t::value_type>(0x80 | ((codepoint >> 12) & 0x3F)));
+                result.append(1, static_cast<typename string_t::value_type>(0x80 | ((codepoint >> 6) & 0x3F)));
+                result.append(1, static_cast<typename string_t::value_type>(0x80 | (codepoint & 0x3F)));
+            }
+            else
+            {
+                throw std::out_of_range("code points above 0x10FFFF are invalid");
+            }
+
+            return result;
+        }
+
+        /// return name of values of type token_type (only used for errors)
+        static std::string token_type_name(const token_type t)
+        {
+            switch (t)
+            {
+                case token_type::uninitialized:
+                    return "<uninitialized>";
+                case token_type::literal_true:
+                    return "true literal";
+                case token_type::literal_false:
+                    return "false literal";
+                case token_type::literal_null:
+                    return "null literal";
+                case token_type::value_string:
+                    return "string literal";
+                case token_type::value_number:
+                    return "number literal";
+                case token_type::begin_array:
+                    return "'['";
+                case token_type::begin_object:
+                    return "'{'";
+                case token_type::end_array:
+                    return "']'";
+                case token_type::end_object:
+                    return "'}'";
+                case token_type::name_separator:
+                    return "':'";
+                case token_type::value_separator:
+                    return "','";
+                case token_type::parse_error:
+                    return "<parse error>";
+                case token_type::end_of_input:
+                    return "end of input";
+                default:
+                {
+                    // catch non-enum values
+                    return "unknown token"; // LCOV_EXCL_LINE
+                }
+            }
+        }
+
+        /*!
+        This function implements a scanner for JSON. It is specified using
+        regular expressions that try to follow RFC 7159 as close as possible.
+        These regular expressions are then translated into a minimized
+        deterministic finite automaton (DFA) by the tool
+        [re2c](http://re2c.org). As a result, the translated code for this
+        function consists of a large block of code with `goto` jumps.
+
+        @return the class of the next token read from the buffer
+
+        @complexity Linear in the length of the input.\n
+
+        Proposition: The loop below will always terminate for finite input.\n
+
+        Proof (by contradiction): Assume a finite input. To loop forever, the
+        loop must never hit code with a `break` statement. The only code
+        snippets without a `break` statement are the continue statements for
+        whitespace and byte-order-marks. To loop forever, the input must be an
+        infinite sequence of whitespace or byte-order-marks. This contradicts
+        the assumption of finite input, q.e.d.
+        */
+        token_type scan()
+        {
+            while (true)
+            {
+                // pointer for backtracking information
+                m_marker = nullptr;
+
+                // remember the begin of the token
+                m_start = m_cursor;
+                assert(m_start != nullptr);
+
+
+                {
+                    lexer_char_t yych;
+                    unsigned int yyaccept = 0;
+                    static const unsigned char yybm[] =
+                    {
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,  32,  32,   0,   0,  32,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        160, 128,   0, 128, 128, 128, 128, 128,
+                        128, 128, 128, 128, 128, 128, 128, 128,
+                        192, 192, 192, 192, 192, 192, 192, 192,
+                        192, 192, 128, 128, 128, 128, 128, 128,
+                        128, 128, 128, 128, 128, 128, 128, 128,
+                        128, 128, 128, 128, 128, 128, 128, 128,
+                        128, 128, 128, 128, 128, 128, 128, 128,
+                        128, 128, 128, 128,   0, 128, 128, 128,
+                        128, 128, 128, 128, 128, 128, 128, 128,
+                        128, 128, 128, 128, 128, 128, 128, 128,
+                        128, 128, 128, 128, 128, 128, 128, 128,
+                        128, 128, 128, 128, 128, 128, 128, 128,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                        0,   0,   0,   0,   0,   0,   0,   0,
+                    };
+                    if ((m_limit - m_cursor) < 5)
+                    {
+                        fill_line_buffer(5);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yybm[0 + yych] & 32)
+                    {
+                        goto basic_json_parser_6;
+                    }
+                    if (yych <= '[')
+                    {
+                        if (yych <= '-')
+                        {
+                            if (yych <= '"')
+                            {
+                                if (yych <= 0x00)
+                                {
+                                    goto basic_json_parser_2;
+                                }
+                                if (yych <= '!')
+                                {
+                                    goto basic_json_parser_4;
+                                }
+                                goto basic_json_parser_9;
+                            }
+                            else
+                            {
+                                if (yych <= '+')
+                                {
+                                    goto basic_json_parser_4;
+                                }
+                                if (yych <= ',')
+                                {
+                                    goto basic_json_parser_10;
+                                }
+                                goto basic_json_parser_12;
+                            }
+                        }
+                        else
+                        {
+                            if (yych <= '9')
+                            {
+                                if (yych <= '/')
+                                {
+                                    goto basic_json_parser_4;
+                                }
+                                if (yych <= '0')
+                                {
+                                    goto basic_json_parser_13;
+                                }
+                                goto basic_json_parser_15;
+                            }
+                            else
+                            {
+                                if (yych <= ':')
+                                {
+                                    goto basic_json_parser_17;
+                                }
+                                if (yych <= 'Z')
+                                {
+                                    goto basic_json_parser_4;
+                                }
+                                goto basic_json_parser_19;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        if (yych <= 'n')
+                        {
+                            if (yych <= 'e')
+                            {
+                                if (yych == ']')
+                                {
+                                    goto basic_json_parser_21;
+                                }
+                                goto basic_json_parser_4;
+                            }
+                            else
+                            {
+                                if (yych <= 'f')
+                                {
+                                    goto basic_json_parser_23;
+                                }
+                                if (yych <= 'm')
+                                {
+                                    goto basic_json_parser_4;
+                                }
+                                goto basic_json_parser_24;
+                            }
+                        }
+                        else
+                        {
+                            if (yych <= 'z')
+                            {
+                                if (yych == 't')
+                                {
+                                    goto basic_json_parser_25;
+                                }
+                                goto basic_json_parser_4;
+                            }
+                            else
+                            {
+                                if (yych <= '{')
+                                {
+                                    goto basic_json_parser_26;
+                                }
+                                if (yych == '}')
+                                {
+                                    goto basic_json_parser_28;
+                                }
+                                goto basic_json_parser_4;
+                            }
+                        }
+                    }
+basic_json_parser_2:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::end_of_input;
+                        break;
+                    }
+basic_json_parser_4:
+                    ++m_cursor;
+basic_json_parser_5:
+                    {
+                        last_token_type = token_type::parse_error;
+                        break;
+                    }
+basic_json_parser_6:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yybm[0 + yych] & 32)
+                    {
+                        goto basic_json_parser_6;
+                    }
+                    {
+                        continue;
+                    }
+basic_json_parser_9:
+                    yyaccept = 0;
+                    yych = *(m_marker = ++m_cursor);
+                    if (yych <= 0x1F)
+                    {
+                        goto basic_json_parser_5;
+                    }
+                    if (yych <= 0x7F)
+                    {
+                        goto basic_json_parser_31;
+                    }
+                    if (yych <= 0xC1)
+                    {
+                        goto basic_json_parser_5;
+                    }
+                    if (yych <= 0xF4)
+                    {
+                        goto basic_json_parser_31;
+                    }
+                    goto basic_json_parser_5;
+basic_json_parser_10:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::value_separator;
+                        break;
+                    }
+basic_json_parser_12:
+                    yych = *++m_cursor;
+                    if (yych <= '/')
+                    {
+                        goto basic_json_parser_5;
+                    }
+                    if (yych <= '0')
+                    {
+                        goto basic_json_parser_13;
+                    }
+                    if (yych <= '9')
+                    {
+                        goto basic_json_parser_15;
+                    }
+                    goto basic_json_parser_5;
+basic_json_parser_13:
+                    yyaccept = 1;
+                    yych = *(m_marker = ++m_cursor);
+                    if (yych <= 'D')
+                    {
+                        if (yych == '.')
+                        {
+                            goto basic_json_parser_43;
+                        }
+                    }
+                    else
+                    {
+                        if (yych <= 'E')
+                        {
+                            goto basic_json_parser_44;
+                        }
+                        if (yych == 'e')
+                        {
+                            goto basic_json_parser_44;
+                        }
+                    }
+basic_json_parser_14:
+                    {
+                        last_token_type = token_type::value_number;
+                        break;
+                    }
+basic_json_parser_15:
+                    yyaccept = 1;
+                    m_marker = ++m_cursor;
+                    if ((m_limit - m_cursor) < 3)
+                    {
+                        fill_line_buffer(3);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yybm[0 + yych] & 64)
+                    {
+                        goto basic_json_parser_15;
+                    }
+                    if (yych <= 'D')
+                    {
+                        if (yych == '.')
+                        {
+                            goto basic_json_parser_43;
+                        }
+                        goto basic_json_parser_14;
+                    }
+                    else
+                    {
+                        if (yych <= 'E')
+                        {
+                            goto basic_json_parser_44;
+                        }
+                        if (yych == 'e')
+                        {
+                            goto basic_json_parser_44;
+                        }
+                        goto basic_json_parser_14;
+                    }
+basic_json_parser_17:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::name_separator;
+                        break;
+                    }
+basic_json_parser_19:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::begin_array;
+                        break;
+                    }
+basic_json_parser_21:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::end_array;
+                        break;
+                    }
+basic_json_parser_23:
+                    yyaccept = 0;
+                    yych = *(m_marker = ++m_cursor);
+                    if (yych == 'a')
+                    {
+                        goto basic_json_parser_45;
+                    }
+                    goto basic_json_parser_5;
+basic_json_parser_24:
+                    yyaccept = 0;
+                    yych = *(m_marker = ++m_cursor);
+                    if (yych == 'u')
+                    {
+                        goto basic_json_parser_46;
+                    }
+                    goto basic_json_parser_5;
+basic_json_parser_25:
+                    yyaccept = 0;
+                    yych = *(m_marker = ++m_cursor);
+                    if (yych == 'r')
+                    {
+                        goto basic_json_parser_47;
+                    }
+                    goto basic_json_parser_5;
+basic_json_parser_26:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::begin_object;
+                        break;
+                    }
+basic_json_parser_28:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::end_object;
+                        break;
+                    }
+basic_json_parser_30:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+basic_json_parser_31:
+                    if (yybm[0 + yych] & 128)
+                    {
+                        goto basic_json_parser_30;
+                    }
+                    if (yych <= 0xE0)
+                    {
+                        if (yych <= '\\')
+                        {
+                            if (yych <= 0x1F)
+                            {
+                                goto basic_json_parser_32;
+                            }
+                            if (yych <= '"')
+                            {
+                                goto basic_json_parser_33;
+                            }
+                            goto basic_json_parser_35;
+                        }
+                        else
+                        {
+                            if (yych <= 0xC1)
+                            {
+                                goto basic_json_parser_32;
+                            }
+                            if (yych <= 0xDF)
+                            {
+                                goto basic_json_parser_36;
+                            }
+                            goto basic_json_parser_37;
+                        }
+                    }
+                    else
+                    {
+                        if (yych <= 0xEF)
+                        {
+                            if (yych == 0xED)
+                            {
+                                goto basic_json_parser_39;
+                            }
+                            goto basic_json_parser_38;
+                        }
+                        else
+                        {
+                            if (yych <= 0xF0)
+                            {
+                                goto basic_json_parser_40;
+                            }
+                            if (yych <= 0xF3)
+                            {
+                                goto basic_json_parser_41;
+                            }
+                            if (yych <= 0xF4)
+                            {
+                                goto basic_json_parser_42;
+                            }
+                        }
+                    }
+basic_json_parser_32:
+                    m_cursor = m_marker;
+                    if (yyaccept == 0)
+                    {
+                        goto basic_json_parser_5;
+                    }
+                    else
+                    {
+                        goto basic_json_parser_14;
+                    }
+basic_json_parser_33:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::value_string;
+                        break;
+                    }
+basic_json_parser_35:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 'e')
+                    {
+                        if (yych <= '/')
+                        {
+                            if (yych == '"')
+                            {
+                                goto basic_json_parser_30;
+                            }
+                            if (yych <= '.')
+                            {
+                                goto basic_json_parser_32;
+                            }
+                            goto basic_json_parser_30;
+                        }
+                        else
+                        {
+                            if (yych <= '\\')
+                            {
+                                if (yych <= '[')
+                                {
+                                    goto basic_json_parser_32;
+                                }
+                                goto basic_json_parser_30;
+                            }
+                            else
+                            {
+                                if (yych == 'b')
+                                {
+                                    goto basic_json_parser_30;
+                                }
+                                goto basic_json_parser_32;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        if (yych <= 'q')
+                        {
+                            if (yych <= 'f')
+                            {
+                                goto basic_json_parser_30;
+                            }
+                            if (yych == 'n')
+                            {
+                                goto basic_json_parser_30;
+                            }
+                            goto basic_json_parser_32;
+                        }
+                        else
+                        {
+                            if (yych <= 's')
+                            {
+                                if (yych <= 'r')
+                                {
+                                    goto basic_json_parser_30;
+                                }
+                                goto basic_json_parser_32;
+                            }
+                            else
+                            {
+                                if (yych <= 't')
+                                {
+                                    goto basic_json_parser_30;
+                                }
+                                if (yych <= 'u')
+                                {
+                                    goto basic_json_parser_48;
+                                }
+                                goto basic_json_parser_32;
+                            }
+                        }
+                    }
+basic_json_parser_36:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 0x7F)
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych <= 0xBF)
+                    {
+                        goto basic_json_parser_30;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_37:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 0x9F)
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych <= 0xBF)
+                    {
+                        goto basic_json_parser_36;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_38:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 0x7F)
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych <= 0xBF)
+                    {
+                        goto basic_json_parser_36;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_39:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 0x7F)
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych <= 0x9F)
+                    {
+                        goto basic_json_parser_36;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_40:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 0x8F)
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych <= 0xBF)
+                    {
+                        goto basic_json_parser_38;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_41:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 0x7F)
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych <= 0xBF)
+                    {
+                        goto basic_json_parser_38;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_42:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 0x7F)
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych <= 0x8F)
+                    {
+                        goto basic_json_parser_38;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_43:
+                    yych = *++m_cursor;
+                    if (yych <= '/')
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych <= '9')
+                    {
+                        goto basic_json_parser_49;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_44:
+                    yych = *++m_cursor;
+                    if (yych <= ',')
+                    {
+                        if (yych == '+')
+                        {
+                            goto basic_json_parser_51;
+                        }
+                        goto basic_json_parser_32;
+                    }
+                    else
+                    {
+                        if (yych <= '-')
+                        {
+                            goto basic_json_parser_51;
+                        }
+                        if (yych <= '/')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= '9')
+                        {
+                            goto basic_json_parser_52;
+                        }
+                        goto basic_json_parser_32;
+                    }
+basic_json_parser_45:
+                    yych = *++m_cursor;
+                    if (yych == 'l')
+                    {
+                        goto basic_json_parser_54;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_46:
+                    yych = *++m_cursor;
+                    if (yych == 'l')
+                    {
+                        goto basic_json_parser_55;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_47:
+                    yych = *++m_cursor;
+                    if (yych == 'u')
+                    {
+                        goto basic_json_parser_56;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_48:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= '@')
+                    {
+                        if (yych <= '/')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= '9')
+                        {
+                            goto basic_json_parser_57;
+                        }
+                        goto basic_json_parser_32;
+                    }
+                    else
+                    {
+                        if (yych <= 'F')
+                        {
+                            goto basic_json_parser_57;
+                        }
+                        if (yych <= '`')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= 'f')
+                        {
+                            goto basic_json_parser_57;
+                        }
+                        goto basic_json_parser_32;
+                    }
+basic_json_parser_49:
+                    yyaccept = 1;
+                    m_marker = ++m_cursor;
+                    if ((m_limit - m_cursor) < 3)
+                    {
+                        fill_line_buffer(3);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= 'D')
+                    {
+                        if (yych <= '/')
+                        {
+                            goto basic_json_parser_14;
+                        }
+                        if (yych <= '9')
+                        {
+                            goto basic_json_parser_49;
+                        }
+                        goto basic_json_parser_14;
+                    }
+                    else
+                    {
+                        if (yych <= 'E')
+                        {
+                            goto basic_json_parser_44;
+                        }
+                        if (yych == 'e')
+                        {
+                            goto basic_json_parser_44;
+                        }
+                        goto basic_json_parser_14;
+                    }
+basic_json_parser_51:
+                    yych = *++m_cursor;
+                    if (yych <= '/')
+                    {
+                        goto basic_json_parser_32;
+                    }
+                    if (yych >= ':')
+                    {
+                        goto basic_json_parser_32;
+                    }
+basic_json_parser_52:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= '/')
+                    {
+                        goto basic_json_parser_14;
+                    }
+                    if (yych <= '9')
+                    {
+                        goto basic_json_parser_52;
+                    }
+                    goto basic_json_parser_14;
+basic_json_parser_54:
+                    yych = *++m_cursor;
+                    if (yych == 's')
+                    {
+                        goto basic_json_parser_58;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_55:
+                    yych = *++m_cursor;
+                    if (yych == 'l')
+                    {
+                        goto basic_json_parser_59;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_56:
+                    yych = *++m_cursor;
+                    if (yych == 'e')
+                    {
+                        goto basic_json_parser_61;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_57:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= '@')
+                    {
+                        if (yych <= '/')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= '9')
+                        {
+                            goto basic_json_parser_63;
+                        }
+                        goto basic_json_parser_32;
+                    }
+                    else
+                    {
+                        if (yych <= 'F')
+                        {
+                            goto basic_json_parser_63;
+                        }
+                        if (yych <= '`')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= 'f')
+                        {
+                            goto basic_json_parser_63;
+                        }
+                        goto basic_json_parser_32;
+                    }
+basic_json_parser_58:
+                    yych = *++m_cursor;
+                    if (yych == 'e')
+                    {
+                        goto basic_json_parser_64;
+                    }
+                    goto basic_json_parser_32;
+basic_json_parser_59:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::literal_null;
+                        break;
+                    }
+basic_json_parser_61:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::literal_true;
+                        break;
+                    }
+basic_json_parser_63:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= '@')
+                    {
+                        if (yych <= '/')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= '9')
+                        {
+                            goto basic_json_parser_66;
+                        }
+                        goto basic_json_parser_32;
+                    }
+                    else
+                    {
+                        if (yych <= 'F')
+                        {
+                            goto basic_json_parser_66;
+                        }
+                        if (yych <= '`')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= 'f')
+                        {
+                            goto basic_json_parser_66;
+                        }
+                        goto basic_json_parser_32;
+                    }
+basic_json_parser_64:
+                    ++m_cursor;
+                    {
+                        last_token_type = token_type::literal_false;
+                        break;
+                    }
+basic_json_parser_66:
+                    ++m_cursor;
+                    if (m_limit <= m_cursor)
+                    {
+                        fill_line_buffer(1);    // LCOV_EXCL_LINE
+                    }
+                    yych = *m_cursor;
+                    if (yych <= '@')
+                    {
+                        if (yych <= '/')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= '9')
+                        {
+                            goto basic_json_parser_30;
+                        }
+                        goto basic_json_parser_32;
+                    }
+                    else
+                    {
+                        if (yych <= 'F')
+                        {
+                            goto basic_json_parser_30;
+                        }
+                        if (yych <= '`')
+                        {
+                            goto basic_json_parser_32;
+                        }
+                        if (yych <= 'f')
+                        {
+                            goto basic_json_parser_30;
+                        }
+                        goto basic_json_parser_32;
+                    }
+                }
+
+            }
+
+            return last_token_type;
+        }
+
+        /*!
+        @brief append data from the stream to the line buffer
+
+        This function is called by the scan() function when the end of the
+        buffer (`m_limit`) is reached and the `m_cursor` pointer cannot be
+        incremented without leaving the limits of the line buffer. Note re2c
+        decides when to call this function.
+
+        If the lexer reads from contiguous storage, there is no trailing null
+        byte. Therefore, this function must make sure to add these padding
+        null bytes.
+
+        If the lexer reads from an input stream, this function reads the next
+        line of the input.
+
+        @pre
+            p p p p p p u u u u u x . . . . . .
+            ^           ^       ^   ^
+            m_content   m_start |   m_limit
+                                m_cursor
+
+        @post
+            u u u u u x x x x x x x . . . . . .
+            ^       ^               ^
+            |       m_cursor        m_limit
+            m_start
+            m_content
+        */
+        void fill_line_buffer(size_t n = 0)
+        {
+            // number of processed characters (p)
+            const auto offset_start = m_start - m_content;
+            // offset for m_marker wrt. to m_start
+            const auto offset_marker = (m_marker == nullptr) ? 0 : m_marker - m_start;
+            // number of unprocessed characters (u)
+            const auto offset_cursor = m_cursor - m_start;
+
+            // no stream is used or end of file is reached
+            if (m_stream == nullptr or m_stream->eof())
+            {
+                // skip this part if we are already using the line buffer
+                if (m_start != reinterpret_cast<const lexer_char_t*>(m_line_buffer.data()))
+                {
+                    // copy unprocessed characters to line buffer
+                    m_line_buffer.clear();
+                    for (m_cursor = m_start; m_cursor != m_limit; ++m_cursor)
+                    {
+                        m_line_buffer.append(1, static_cast<const char>(*m_cursor));
+                    }
+                }
+
+                // append n characters to make sure that there is sufficient
+                // space between m_cursor and m_limit
+                m_line_buffer.append(1, '\x00');
+                m_line_buffer.append(n - 1, '\x01');
+            }
+            else
+            {
+                // delete processed characters from line buffer
+                m_line_buffer.erase(0, static_cast<size_t>(offset_start));
+                // read next line from input stream
+                std::string line;
+                std::getline(*m_stream, line, '\n');
+                // add line with newline symbol to the line buffer
+                m_line_buffer += line + "\n";
+            }
+
+            // set pointers
+            m_content = reinterpret_cast<const lexer_char_t*>(m_line_buffer.c_str());
+            assert(m_content != nullptr);
+            m_start  = m_content;
+            m_marker = m_start + offset_marker;
+            m_cursor = m_start + offset_cursor;
+            m_limit  = m_start + m_line_buffer.size();
+        }
+
+        /// return string representation of last read token
+        string_t get_token_string() const
+        {
+            assert(m_start != nullptr);
+            return string_t(reinterpret_cast<typename string_t::const_pointer>(m_start),
+                            static_cast<size_t>(m_cursor - m_start));
+        }
+
+        /*!
+        @brief return string value for string tokens
+
+        The function iterates the characters between the opening and closing
+        quotes of the string value. The complete string is the range
+        [m_start,m_cursor). Consequently, we iterate from m_start+1 to
+        m_cursor-1.
+
+        We differentiate two cases:
+
+        1. Escaped characters. In this case, a new character is constructed
+           according to the nature of the escape. Some escapes create new
+           characters (e.g., `"\\n"` is replaced by `"\n"`), some are copied
+           as is (e.g., `"\\\\"`). Furthermore, Unicode escapes of the shape
+           `"\\uxxxx"` need special care. In this case, to_unicode takes care
+           of the construction of the values.
+        2. Unescaped characters are copied as is.
+
+        @pre `m_cursor - m_start >= 2`, meaning the length of the last token
+        is at least 2 bytes which is trivially true for any string (which
+        consists of at least two quotes).
+
+            " c1 c2 c3 ... "
+            ^                ^
+            m_start          m_cursor
+
+        @complexity Linear in the length of the string.\n
+
+        Lemma: The loop body will always terminate.\n
+
+        Proof (by contradiction): Assume the loop body does not terminate. As
+        the loop body does not contain another loop, one of the called
+        functions must never return. The called functions are `std::strtoul`
+        and to_unicode. Neither function can loop forever, so the loop body
+        will never loop forever which contradicts the assumption that the loop
+        body does not terminate, q.e.d.\n
+
+        Lemma: The loop condition for the for loop is eventually false.\n
+
+        Proof (by contradiction): Assume the loop does not terminate. Due to
+        the above lemma, this can only be due to a tautological loop
+        condition; that is, the loop condition i < m_cursor - 1 must always be
+        true. Let x be the change of i for any loop iteration. Then
+        m_start + 1 + x < m_cursor - 1 must hold to loop indefinitely. This
+        can be rephrased to m_cursor - m_start - 2 > x. With the
+        precondition, we x <= 0, meaning that the loop condition holds
+        indefinitly if i is always decreased. However, observe that the value
+        of i is strictly increasing with each iteration, as it is incremented
+        by 1 in the iteration expression and never decremented inside the loop
+        body. Hence, the loop condition will eventually be false which
+        contradicts the assumption that the loop condition is a tautology,
+        q.e.d.
+
+        @return string value of current token without opening and closing
+        quotes
+        @throw std::out_of_range if to_unicode fails
+        */
+        string_t get_string() const
+        {
+            assert(m_cursor - m_start >= 2);
+
+            string_t result;
+            result.reserve(static_cast<size_t>(m_cursor - m_start - 2));
+
+            // iterate the result between the quotes
+            for (const lexer_char_t* i = m_start + 1; i < m_cursor - 1; ++i)
+            {
+                // process escaped characters
+                if (*i == '\\')
+                {
+                    // read next character
+                    ++i;
+
+                    switch (*i)
+                    {
+                        // the default escapes
+                        case 't':
+                        {
+                            result += "\t";
+                            break;
+                        }
+                        case 'b':
+                        {
+                            result += "\b";
+                            break;
+                        }
+                        case 'f':
+                        {
+                            result += "\f";
+                            break;
+                        }
+                        case 'n':
+                        {
+                            result += "\n";
+                            break;
+                        }
+                        case 'r':
+                        {
+                            result += "\r";
+                            break;
+                        }
+                        case '\\':
+                        {
+                            result += "\\";
+                            break;
+                        }
+                        case '/':
+                        {
+                            result += "/";
+                            break;
+                        }
+                        case '"':
+                        {
+                            result += "\"";
+                            break;
+                        }
+
+                        // unicode
+                        case 'u':
+                        {
+                            // get code xxxx from uxxxx
+                            auto codepoint = std::strtoul(std::string(reinterpret_cast<typename string_t::const_pointer>(i + 1),
+                                                          4).c_str(), nullptr, 16);
+
+                            // check if codepoint is a high surrogate
+                            if (codepoint >= 0xD800 and codepoint <= 0xDBFF)
+                            {
+                                // make sure there is a subsequent unicode
+                                if ((i + 6 >= m_limit) or * (i + 5) != '\\' or * (i + 6) != 'u')
+                                {
+                                    throw std::invalid_argument("missing low surrogate");
+                                }
+
+                                // get code yyyy from uxxxx\uyyyy
+                                auto codepoint2 = std::strtoul(std::string(reinterpret_cast<typename string_t::const_pointer>
+                                                               (i + 7), 4).c_str(), nullptr, 16);
+                                result += to_unicode(codepoint, codepoint2);
+                                // skip the next 10 characters (xxxx\uyyyy)
+                                i += 10;
+                            }
+                            else if (codepoint >= 0xDC00 and codepoint <= 0xDFFF)
+                            {
+                                // we found a lone low surrogate
+                                throw std::invalid_argument("missing high surrogate");
+                            }
+                            else
+                            {
+                                // add unicode character(s)
+                                result += to_unicode(codepoint);
+                                // skip the next four characters (xxxx)
+                                i += 4;
+                            }
+                            break;
+                        }
+                    }
+                }
+                else
+                {
+                    // all other characters are just copied to the end of the
+                    // string
+                    result.append(1, static_cast<typename string_t::value_type>(*i));
+                }
+            }
+
+            return result;
+        }
+
+        /*!
+        @brief parse floating point number
+
+        This function (and its overloads) serves to select the most approprate
+        standard floating point number parsing function based on the type
+        supplied via the first parameter.  Set this to @a
+        static_cast<number_float_t*>(nullptr).
+
+        @param[in] type  the @ref number_float_t in use
+
+        @param[in,out] endptr recieves a pointer to the first character after
+        the number
+
+        @return the floating point number
+        */
+        long double str_to_float_t(long double* /* type */, char** endptr) const
+        {
+            return std::strtold(reinterpret_cast<typename string_t::const_pointer>(m_start), endptr);
+        }
+
+        /*!
+        @brief parse floating point number
+
+        This function (and its overloads) serves to select the most approprate
+        standard floating point number parsing function based on the type
+        supplied via the first parameter.  Set this to @a
+        static_cast<number_float_t*>(nullptr).
+
+        @param[in] type  the @ref number_float_t in use
+
+        @param[in,out] endptr  recieves a pointer to the first character after
+        the number
+
+        @return the floating point number
+        */
+        double str_to_float_t(double* /* type */, char** endptr) const
+        {
+            return std::strtod(reinterpret_cast<typename string_t::const_pointer>(m_start), endptr);
+        }
+
+        /*!
+        @brief parse floating point number
+
+        This function (and its overloads) serves to select the most approprate
+        standard floating point number parsing function based on the type
+        supplied via the first parameter.  Set this to @a
+        static_cast<number_float_t*>(nullptr).
+
+        @param[in] type  the @ref number_float_t in use
+
+        @param[in,out] endptr  recieves a pointer to the first character after
+        the number
+
+        @return the floating point number
+        */
+        float str_to_float_t(float* /* type */, char** endptr) const
+        {
+            return std::strtof(reinterpret_cast<typename string_t::const_pointer>(m_start), endptr);
+        }
+
+        /*!
+        @brief return number value for number tokens
+
+        This function translates the last token into the most appropriate
+        number type (either integer, unsigned integer or floating point),
+        which is passed back to the caller via the result parameter.
+
+        This function parses the integer component up to the radix point or
+        exponent while collecting information about the 'floating point
+        representation', which it stores in the result parameter. If there is
+        no radix point or exponent, and the number can fit into a @ref
+        number_integer_t or @ref number_unsigned_t then it sets the result
+        parameter accordingly.
+
+        If the number is a floating point number the number is then parsed
+        using @a std:strtod (or @a std:strtof or @a std::strtold).
+
+        @param[out] result  @ref basic_json object to receive the number, or
+        NAN if the conversion read past the current token. The latter case
+        needs to be treated by the caller function.
+        */
+        void get_number(basic_json& result) const
+        {
+            assert(m_start != nullptr);
+
+            const lexer::lexer_char_t* curptr = m_start;
+
+            // accumulate the integer conversion result (unsigned for now)
+            number_unsigned_t value = 0;
+
+            // maximum absolute value of the relevant integer type
+            number_unsigned_t max;
+
+            // temporarily store the type to avoid unecessary bitfield access
+            value_t type;
+
+            // look for sign
+            if (*curptr == '-')
+            {
+                type = value_t::number_integer;
+                max = static_cast<uint64_t>((std::numeric_limits<number_integer_t>::max)()) + 1;
+                curptr++;
+            }
+            else
+            {
+                type = value_t::number_unsigned;
+                max = static_cast<uint64_t>((std::numeric_limits<number_unsigned_t>::max)());
+            }
+
+            // count the significant figures
+            for (; curptr < m_cursor; curptr++)
+            {
+                // quickly skip tests if a digit
+                if (*curptr < '0' || *curptr > '9')
+                {
+                    if (*curptr == '.')
+                    {
+                        // don't count '.' but change to float
+                        type = value_t::number_float;
+                        continue;
+                    }
+                    // assume exponent (if not then will fail parse): change to
+                    // float, stop counting and record exponent details
+                    type = value_t::number_float;
+                    break;
+                }
+
+                // skip if definitely not an integer
+                if (type != value_t::number_float)
+                {
+                    // multiply last value by ten and add the new digit
+                    auto temp = value * 10 + *curptr - '0';
+
+                    // test for overflow
+                    if (temp < value || temp > max)
+                    {
+                        // overflow
+                        type = value_t::number_float;
+                    }
+                    else
+                    {
+                        // no overflow - save it
+                        value = temp;
+                    }
+                }
+            }
+
+            // save the value (if not a float)
+            if (type == value_t::number_unsigned)
+            {
+                result.m_value.number_unsigned = value;
+            }
+            else if (type == value_t::number_integer)
+            {
+                result.m_value.number_integer = -static_cast<number_integer_t>(value);
+            }
+            else
+            {
+                // parse with strtod
+                result.m_value.number_float = str_to_float_t(static_cast<number_float_t*>(nullptr), NULL);
+
+                // replace infinity and NAN by null
+                if (not std::isfinite(result.m_value.number_float))
+                {
+                    type = value_t::null;
+                    result.m_value = basic_json::json_value();
+                }
+            }
+
+            // save the type
+            result.m_type = type;
+        }
+
+      private:
+        /// optional input stream
+        std::istream* m_stream = nullptr;
+        /// line buffer buffer for m_stream
+        string_t m_line_buffer {};
+        /// the buffer pointer
+        const lexer_char_t* m_content = nullptr;
+        /// pointer to the beginning of the current symbol
+        const lexer_char_t* m_start = nullptr;
+        /// pointer for backtracking information
+        const lexer_char_t* m_marker = nullptr;
+        /// pointer to the current symbol
+        const lexer_char_t* m_cursor = nullptr;
+        /// pointer to the end of the buffer
+        const lexer_char_t* m_limit = nullptr;
+        /// the last token type
+        token_type last_token_type = token_type::end_of_input;
+    };
+
+    /*!
+    @brief syntax analysis
+
+    This class implements a recursive decent parser.
+    */
+    class parser
+    {
+      public:
+        /// a parser reading from a string literal
+        parser(const char* buff, const parser_callback_t cb = nullptr)
+            : callback(cb),
+              m_lexer(reinterpret_cast<const typename lexer::lexer_char_t*>(buff), strlen(buff))
+        {}
+
+        /// a parser reading from an input stream
+        parser(std::istream& is, const parser_callback_t cb = nullptr)
+            : callback(cb), m_lexer(is)
+        {}
+
+        /// a parser reading from an iterator range with contiguous storage
+        template<class IteratorType, typename std::enable_if<
+                     std::is_same<typename std::iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value
+                     , int>::type
+                 = 0>
+        parser(IteratorType first, IteratorType last, const parser_callback_t cb = nullptr)
+            : callback(cb),
+              m_lexer(reinterpret_cast<const typename lexer::lexer_char_t*>(&(*first)),
+                      static_cast<size_t>(std::distance(first, last)))
+        {}
+
+        /// public parser interface
+        basic_json parse()
+        {
+            // read first token
+            get_token();
+
+            basic_json result = parse_internal(true);
+            result.assert_invariant();
+
+            expect(lexer::token_type::end_of_input);
+
+            // return parser result and replace it with null in case the
+            // top-level value was discarded by the callback function
+            return result.is_discarded() ? basic_json() : std::move(result);
+        }
+
+      private:
+        /// the actual parser
+        basic_json parse_internal(bool keep)
+        {
+            auto result = basic_json(value_t::discarded);
+
+            switch (last_token)
+            {
+                case lexer::token_type::begin_object:
+                {
+                    if (keep and (not callback
+                                  or ((keep = callback(depth++, parse_event_t::object_start, result)) != 0)))
+                    {
+                        // explicitly set result to object to cope with {}
+                        result.m_type = value_t::object;
+                        result.m_value = value_t::object;
+                    }
+
+                    // read next token
+                    get_token();
+
+                    // closing } -> we are done
+                    if (last_token == lexer::token_type::end_object)
+                    {
+                        get_token();
+                        if (keep and callback and not callback(--depth, parse_event_t::object_end, result))
+                        {
+                            result = basic_json(value_t::discarded);
+                        }
+                        return result;
+                    }
+
+                    // no comma is expected here
+                    unexpect(lexer::token_type::value_separator);
+
+                    // otherwise: parse key-value pairs
+                    do
+                    {
+                        // ugly, but could be fixed with loop reorganization
+                        if (last_token == lexer::token_type::value_separator)
+                        {
+                            get_token();
+                        }
+
+                        // store key
+                        expect(lexer::token_type::value_string);
+                        const auto key = m_lexer.get_string();
+
+                        bool keep_tag = false;
+                        if (keep)
+                        {
+                            if (callback)
+                            {
+                                basic_json k(key);
+                                keep_tag = callback(depth, parse_event_t::key, k);
+                            }
+                            else
+                            {
+                                keep_tag = true;
+                            }
+                        }
+
+                        // parse separator (:)
+                        get_token();
+                        expect(lexer::token_type::name_separator);
+
+                        // parse and add value
+                        get_token();
+                        auto value = parse_internal(keep);
+                        if (keep and keep_tag and not value.is_discarded())
+                        {
+                            result[key] = std::move(value);
+                        }
+                    }
+                    while (last_token == lexer::token_type::value_separator);
+
+                    // closing }
+                    expect(lexer::token_type::end_object);
+                    get_token();
+                    if (keep and callback and not callback(--depth, parse_event_t::object_end, result))
+                    {
+                        result = basic_json(value_t::discarded);
+                    }
+
+                    return result;
+                }
+
+                case lexer::token_type::begin_array:
+                {
+                    if (keep and (not callback
+                                  or ((keep = callback(depth++, parse_event_t::array_start, result)) != 0)))
+                    {
+                        // explicitly set result to object to cope with []
+                        result.m_type = value_t::array;
+                        result.m_value = value_t::array;
+                    }
+
+                    // read next token
+                    get_token();
+
+                    // closing ] -> we are done
+                    if (last_token == lexer::token_type::end_array)
+                    {
+                        get_token();
+                        if (callback and not callback(--depth, parse_event_t::array_end, result))
+                        {
+                            result = basic_json(value_t::discarded);
+                        }
+                        return result;
+                    }
+
+                    // no comma is expected here
+                    unexpect(lexer::token_type::value_separator);
+
+                    // otherwise: parse values
+                    do
+                    {
+                        // ugly, but could be fixed with loop reorganization
+                        if (last_token == lexer::token_type::value_separator)
+                        {
+                            get_token();
+                        }
+
+                        // parse value
+                        auto value = parse_internal(keep);
+                        if (keep and not value.is_discarded())
+                        {
+                            result.push_back(std::move(value));
+                        }
+                    }
+                    while (last_token == lexer::token_type::value_separator);
+
+                    // closing ]
+                    expect(lexer::token_type::end_array);
+                    get_token();
+                    if (keep and callback and not callback(--depth, parse_event_t::array_end, result))
+                    {
+                        result = basic_json(value_t::discarded);
+                    }
+
+                    return result;
+                }
+
+                case lexer::token_type::literal_null:
+                {
+                    get_token();
+                    result.m_type = value_t::null;
+                    break;
+                }
+
+                case lexer::token_type::value_string:
+                {
+                    const auto s = m_lexer.get_string();
+                    get_token();
+                    result = basic_json(s);
+                    break;
+                }
+
+                case lexer::token_type::literal_true:
+                {
+                    get_token();
+                    result.m_type = value_t::boolean;
+                    result.m_value = true;
+                    break;
+                }
+
+                case lexer::token_type::literal_false:
+                {
+                    get_token();
+                    result.m_type = value_t::boolean;
+                    result.m_value = false;
+                    break;
+                }
+
+                case lexer::token_type::value_number:
+                {
+                    m_lexer.get_number(result);
+                    get_token();
+                    break;
+                }
+
+                default:
+                {
+                    // the last token was unexpected
+                    unexpect(last_token);
+                }
+            }
+
+            if (keep and callback and not callback(depth, parse_event_t::value, result))
+            {
+                result = basic_json(value_t::discarded);
+            }
+            return result;
+        }
+
+        /// get next token from lexer
+        typename lexer::token_type get_token()
+        {
+            last_token = m_lexer.scan();
+            return last_token;
+        }
+
+        void expect(typename lexer::token_type t) const
+        {
+            if (t != last_token)
+            {
+                std::string error_msg = "parse error - unexpected ";
+                error_msg += (last_token == lexer::token_type::parse_error ? ("'" +  m_lexer.get_token_string() +
+                              "'") :
+                              lexer::token_type_name(last_token));
+                error_msg += "; expected " + lexer::token_type_name(t);
+                throw std::invalid_argument(error_msg);
+            }
+        }
+
+        void unexpect(typename lexer::token_type t) const
+        {
+            if (t == last_token)
+            {
+                std::string error_msg = "parse error - unexpected ";
+                error_msg += (last_token == lexer::token_type::parse_error ? ("'" +  m_lexer.get_token_string() +
+                              "'") :
+                              lexer::token_type_name(last_token));
+                throw std::invalid_argument(error_msg);
+            }
+        }
+
+      private:
+        /// current level of recursion
+        int depth = 0;
+        /// callback function
+        const parser_callback_t callback = nullptr;
+        /// the type of the last read token
+        typename lexer::token_type last_token = lexer::token_type::uninitialized;
+        /// the lexer
+        lexer m_lexer;
+    };
+
+  public:
+    /*!
+    @brief JSON Pointer
+
+    A JSON pointer defines a string syntax for identifying a specific value
+    within a JSON document. It can be used with functions `at` and
+    `operator[]`. Furthermore, JSON pointers are the base for JSON patches.
+
+    @sa [RFC 6901](https://tools.ietf.org/html/rfc6901)
+
+    @since version 2.0.0
+    */
+    class json_pointer
+    {
+        /// allow basic_json to access private members
+        friend class basic_json;
+
+      public:
+        /*!
+        @brief create JSON pointer
+
+        Create a JSON pointer according to the syntax described in
+        [Section 3 of RFC6901](https://tools.ietf.org/html/rfc6901#section-3).
+
+        @param[in] s  string representing the JSON pointer; if omitted, the
+                      empty string is assumed which references the whole JSON
+                      value
+
+        @throw std::domain_error if reference token is nonempty and does not
+        begin with a slash (`/`); example: `"JSON pointer must be empty or
+        begin with /"`
+        @throw std::domain_error if a tilde (`~`) is not followed by `0`
+        (representing `~`) or `1` (representing `/`); example: `"escape error:
+        ~ must be followed with 0 or 1"`
+
+        @liveexample{The example shows the construction several valid JSON
+        pointers as well as the exceptional behavior.,json_pointer}
+
+        @since version 2.0.0
+        */
+        explicit json_pointer(const std::string& s = "")
+            : reference_tokens(split(s))
+        {}
+
+        /*!
+        @brief return a string representation of the JSON pointer
+
+        @invariant For each JSON pointer `ptr`, it holds:
+        @code {.cpp}
+        ptr == json_pointer(ptr.to_string());
+        @endcode
+
+        @return a string representation of the JSON pointer
+
+        @liveexample{The example shows the result of `to_string`.,
+        json_pointer__to_string}
+
+        @since version 2.0.0
+        */
+        std::string to_string() const noexcept
+        {
+            return std::accumulate(reference_tokens.begin(),
+                                   reference_tokens.end(), std::string{},
+                                   [](const std::string & a, const std::string & b)
+            {
+                return a + "/" + escape(b);
+            });
+        }
+
+        /// @copydoc to_string()
+        operator std::string() const
+        {
+            return to_string();
+        }
+
+      private:
+        /// remove and return last reference pointer
+        std::string pop_back()
+        {
+            if (is_root())
+            {
+                throw std::domain_error("JSON pointer has no parent");
+            }
+
+            auto last = reference_tokens.back();
+            reference_tokens.pop_back();
+            return last;
+        }
+
+        /// return whether pointer points to the root document
+        bool is_root() const
+        {
+            return reference_tokens.empty();
+        }
+
+        json_pointer top() const
+        {
+            if (is_root())
+            {
+                throw std::domain_error("JSON pointer has no parent");
+            }
+
+            json_pointer result = *this;
+            result.reference_tokens = {reference_tokens[0]};
+            return result;
+        }
+
+        /*!
+        @brief create and return a reference to the pointed to value
+
+        @complexity Linear in the number of reference tokens.
+        */
+        reference get_and_create(reference j) const
+        {
+            pointer result = &j;
+
+            // in case no reference tokens exist, return a reference to the
+            // JSON value j which will be overwritten by a primitive value
+            for (const auto& reference_token : reference_tokens)
+            {
+                switch (result->m_type)
+                {
+                    case value_t::null:
+                    {
+                        if (reference_token == "0")
+                        {
+                            // start a new array if reference token is 0
+                            result = &result->operator[](0);
+                        }
+                        else
+                        {
+                            // start a new object otherwise
+                            result = &result->operator[](reference_token);
+                        }
+                        break;
+                    }
+
+                    case value_t::object:
+                    {
+                        // create an entry in the object
+                        result = &result->operator[](reference_token);
+                        break;
+                    }
+
+                    case value_t::array:
+                    {
+                        // create an entry in the array
+                        result = &result->operator[](static_cast<size_type>(std::stoi(reference_token)));
+                        break;
+                    }
+
+                    /*
+                    The following code is only reached if there exists a
+                    reference token _and_ the current value is primitive. In
+                    this case, we have an error situation, because primitive
+                    values may only occur as single value; that is, with an
+                    empty list of reference tokens.
+                    */
+                    default:
+                    {
+                        throw std::domain_error("invalid value to unflatten");
+                    }
+                }
+            }
+
+            return *result;
+        }
+
+        /*!
+        @brief return a reference to the pointed to value
+
+        @note This version does not throw if a value is not present, but tries
+        to create nested values instead. For instance, calling this function
+        with pointer `"/this/that"` on a null value is equivalent to calling
+        `operator[]("this").operator[]("that")` on that value, effectively
+        changing the null value to an object.
+
+        @param[in] ptr  a JSON value
+
+        @return reference to the JSON value pointed to by the JSON pointer
+
+        @complexity Linear in the length of the JSON pointer.
+
+        @throw std::out_of_range      if the JSON pointer can not be resolved
+        @throw std::domain_error      if an array index begins with '0'
+        @throw std::invalid_argument  if an array index was not a number
+        */
+        reference get_unchecked(pointer ptr) const
+        {
+            for (const auto& reference_token : reference_tokens)
+            {
+                // convert null values to arrays or objects before continuing
+                if (ptr->m_type == value_t::null)
+                {
+                    // check if reference token is a number
+                    const bool nums = std::all_of(reference_token.begin(),
+                                                  reference_token.end(),
+                                                  [](const char x)
+                    {
+                        return std::isdigit(x);
+                    });
+
+                    // change value to array for numbers or "-" or to object
+                    // otherwise
+                    if (nums or reference_token == "-")
+                    {
+                        *ptr = value_t::array;
+                    }
+                    else
+                    {
+                        *ptr = value_t::object;
+                    }
+                }
+
+                switch (ptr->m_type)
+                {
+                    case value_t::object:
+                    {
+                        // use unchecked object access
+                        ptr = &ptr->operator[](reference_token);
+                        break;
+                    }
+
+                    case value_t::array:
+                    {
+                        // error condition (cf. RFC 6901, Sect. 4)
+                        if (reference_token.size() > 1 and reference_token[0] == '0')
+                        {
+                            throw std::domain_error("array index must not begin with '0'");
+                        }
+
+                        if (reference_token == "-")
+                        {
+                            // explicityly treat "-" as index beyond the end
+                            ptr = &ptr->operator[](ptr->m_value.array->size());
+                        }
+                        else
+                        {
+                            // convert array index to number; unchecked access
+                            ptr = &ptr->operator[](static_cast<size_type>(std::stoi(reference_token)));
+                        }
+                        break;
+                    }
+
+                    default:
+                    {
+                        throw std::out_of_range("unresolved reference token '" + reference_token + "'");
+                    }
+                }
+            }
+
+            return *ptr;
+        }
+
+        reference get_checked(pointer ptr) const
+        {
+            for (const auto& reference_token : reference_tokens)
+            {
+                switch (ptr->m_type)
+                {
+                    case value_t::object:
+                    {
+                        // note: at performs range check
+                        ptr = &ptr->at(reference_token);
+                        break;
+                    }
+
+                    case value_t::array:
+                    {
+                        if (reference_token == "-")
+                        {
+                            // "-" always fails the range check
+                            throw std::out_of_range("array index '-' (" +
+                                                    std::to_string(ptr->m_value.array->size()) +
+                                                    ") is out of range");
+                        }
+
+                        // error condition (cf. RFC 6901, Sect. 4)
+                        if (reference_token.size() > 1 and reference_token[0] == '0')
+                        {
+                            throw std::domain_error("array index must not begin with '0'");
+                        }
+
+                        // note: at performs range check
+                        ptr = &ptr->at(static_cast<size_type>(std::stoi(reference_token)));
+                        break;
+                    }
+
+                    default:
+                    {
+                        throw std::out_of_range("unresolved reference token '" + reference_token + "'");
+                    }
+                }
+            }
+
+            return *ptr;
+        }
+
+        /*!
+        @brief return a const reference to the pointed to value
+
+        @param[in] ptr  a JSON value
+
+        @return const reference to the JSON value pointed to by the JSON
+                pointer
+        */
+        const_reference get_unchecked(const_pointer ptr) const
+        {
+            for (const auto& reference_token : reference_tokens)
+            {
+                switch (ptr->m_type)
+                {
+                    case value_t::object:
+                    {
+                        // use unchecked object access
+                        ptr = &ptr->operator[](reference_token);
+                        break;
+                    }
+
+                    case value_t::array:
+                    {
+                        if (reference_token == "-")
+                        {
+                            // "-" cannot be used for const access
+                            throw std::out_of_range("array index '-' (" +
+                                                    std::to_string(ptr->m_value.array->size()) +
+                                                    ") is out of range");
+                        }
+
+                        // error condition (cf. RFC 6901, Sect. 4)
+                        if (reference_token.size() > 1 and reference_token[0] == '0')
+                        {
+                            throw std::domain_error("array index must not begin with '0'");
+                        }
+
+                        // use unchecked array access
+                        ptr = &ptr->operator[](static_cast<size_type>(std::stoi(reference_token)));
+                        break;
+                    }
+
+                    default:
+                    {
+                        throw std::out_of_range("unresolved reference token '" + reference_token + "'");
+                    }
+                }
+            }
+
+            return *ptr;
+        }
+
+        const_reference get_checked(const_pointer ptr) const
+        {
+            for (const auto& reference_token : reference_tokens)
+            {
+                switch (ptr->m_type)
+                {
+                    case value_t::object:
+                    {
+                        // note: at performs range check
+                        ptr = &ptr->at(reference_token);
+                        break;
+                    }
+
+                    case value_t::array:
+                    {
+                        if (reference_token == "-")
+                        {
+                            // "-" always fails the range check
+                            throw std::out_of_range("array index '-' (" +
+                                                    std::to_string(ptr->m_value.array->size()) +
+                                                    ") is out of range");
+                        }
+
+                        // error condition (cf. RFC 6901, Sect. 4)
+                        if (reference_token.size() > 1 and reference_token[0] == '0')
+                        {
+                            throw std::domain_error("array index must not begin with '0'");
+                        }
+
+                        // note: at performs range check
+                        ptr = &ptr->at(static_cast<size_type>(std::stoi(reference_token)));
+                        break;
+                    }
+
+                    default:
+                    {
+                        throw std::out_of_range("unresolved reference token '" + reference_token + "'");
+                    }
+                }
+            }
+
+            return *ptr;
+        }
+
+        /// split the string input to reference tokens
+        static std::vector<std::string> split(const std::string& reference_string)
+        {
+            std::vector<std::string> result;
+
+            // special case: empty reference string -> no reference tokens
+            if (reference_string.empty())
+            {
+                return result;
+            }
+
+            // check if nonempty reference string begins with slash
+            if (reference_string[0] != '/')
+            {
+                throw std::domain_error("JSON pointer must be empty or begin with '/'");
+            }
+
+            // extract the reference tokens:
+            // - slash: position of the last read slash (or end of string)
+            // - start: position after the previous slash
+            for (
+                // search for the first slash after the first character
+                size_t slash = reference_string.find_first_of("/", 1),
+                // set the beginning of the first reference token
+                start = 1;
+                // we can stop if start == string::npos+1 = 0
+                start != 0;
+                // set the beginning of the next reference token
+                // (will eventually be 0 if slash == std::string::npos)
+                start = slash + 1,
+                // find next slash
+                slash = reference_string.find_first_of("/", start))
+            {
+                // use the text between the beginning of the reference token
+                // (start) and the last slash (slash).
+                auto reference_token = reference_string.substr(start, slash - start);
+
+                // check reference tokens are properly escaped
+                for (size_t pos = reference_token.find_first_of("~");
+                        pos != std::string::npos;
+                        pos = reference_token.find_first_of("~", pos + 1))
+                {
+                    assert(reference_token[pos] == '~');
+
+                    // ~ must be followed by 0 or 1
+                    if (pos == reference_token.size() - 1 or
+                            (reference_token[pos + 1] != '0' and
+                             reference_token[pos + 1] != '1'))
+                    {
+                        throw std::domain_error("escape error: '~' must be followed with '0' or '1'");
+                    }
+                }
+
+                // finally, store the reference token
+                unescape(reference_token);
+                result.push_back(reference_token);
+            }
+
+            return result;
+        }
+
+      private:
+        /*!
+        @brief replace all occurrences of a substring by another string
+
+        @param[in,out] s  the string to manipulate
+        @param[in]     f  the substring to replace with @a t
+        @param[in]     t  the string to replace @a f
+
+        @return The string @a s where all occurrences of @a f are replaced
+                with @a t.
+
+        @pre The search string @a f must not be empty.
+
+        @since version 2.0.0
+        */
+        static void replace_substring(std::string& s,
+                                      const std::string& f,
+                                      const std::string& t)
+        {
+            assert(not f.empty());
+
+            for (
+                size_t pos = s.find(f);         // find first occurrence of f
+                pos != std::string::npos;       // make sure f was found
+                s.replace(pos, f.size(), t),    // replace with t
+                pos = s.find(f, pos + t.size()) // find next occurrence of f
+            );
+        }
+
+        /// escape tilde and slash
+        static std::string escape(std::string s)
+        {
+            // escape "~"" to "~0" and "/" to "~1"
+            replace_substring(s, "~", "~0");
+            replace_substring(s, "/", "~1");
+            return s;
+        }
+
+        /// unescape tilde and slash
+        static void unescape(std::string& s)
+        {
+            // first transform any occurrence of the sequence '~1' to '/'
+            replace_substring(s, "~1", "/");
+            // then transform any occurrence of the sequence '~0' to '~'
+            replace_substring(s, "~0", "~");
+        }
+
+        /*!
+        @param[in] reference_string  the reference string to the current value
+        @param[in] value             the value to consider
+        @param[in,out] result        the result object to insert values to
+
+        @note Empty objects or arrays are flattened to `null`.
+        */
+        static void flatten(const std::string& reference_string,
+                            const basic_json& value,
+                            basic_json& result)
+        {
+            switch (value.m_type)
+            {
+                case value_t::array:
+                {
+                    if (value.m_value.array->empty())
+                    {
+                        // flatten empty array as null
+                        result[reference_string] = nullptr;
+                    }
+                    else
+                    {
+                        // iterate array and use index as reference string
+                        for (size_t i = 0; i < value.m_value.array->size(); ++i)
+                        {
+                            flatten(reference_string + "/" + std::to_string(i),
+                                    value.m_value.array->operator[](i), result);
+                        }
+                    }
+                    break;
+                }
+
+                case value_t::object:
+                {
+                    if (value.m_value.object->empty())
+                    {
+                        // flatten empty object as null
+                        result[reference_string] = nullptr;
+                    }
+                    else
+                    {
+                        // iterate object and use keys as reference string
+                        for (const auto& element : *value.m_value.object)
+                        {
+                            flatten(reference_string + "/" + escape(element.first),
+                                    element.second, result);
+                        }
+                    }
+                    break;
+                }
+
+                default:
+                {
+                    // add primitive value with its reference string
+                    result[reference_string] = value;
+                    break;
+                }
+            }
+        }
+
+        /*!
+        @param[in] value  flattened JSON
+
+        @return unflattened JSON
+        */
+        static basic_json unflatten(const basic_json& value)
+        {
+            if (not value.is_object())
+            {
+                throw std::domain_error("only objects can be unflattened");
+            }
+
+            basic_json result;
+
+            // iterate the JSON object values
+            for (const auto& element : *value.m_value.object)
+            {
+                if (not element.second.is_primitive())
+                {
+                    throw std::domain_error("values in object must be primitive");
+                }
+
+                // assign value to reference pointed to by JSON pointer; Note
+                // that if the JSON pointer is "" (i.e., points to the whole
+                // value), function get_and_create returns a reference to
+                // result itself. An assignment will then create a primitive
+                // value.
+                json_pointer(element.first).get_and_create(result) = element.second;
+            }
+
+            return result;
+        }
+
+      private:
+        /// the reference tokens
+        std::vector<std::string> reference_tokens {};
+    };
+
+    //////////////////////////
+    // JSON Pointer support //
+    //////////////////////////
+
+    /// @name JSON Pointer functions
+    /// @{
+
+    /*!
+    @brief access specified element via JSON Pointer
+
+    Uses a JSON pointer to retrieve a reference to the respective JSON value.
+    No bound checking is performed. Similar to @ref operator[](const typename
+    object_t::key_type&), `null` values are created in arrays and objects if
+    necessary.
+
+    In particular:
+    - If the JSON pointer points to an object key that does not exist, it
+      is created an filled with a `null` value before a reference to it
+      is returned.
+    - If the JSON pointer points to an array index that does not exist, it
+      is created an filled with a `null` value before a reference to it
+      is returned. All indices between the current maximum and the given
+      index are also filled with `null`.
+    - The special value `-` is treated as a synonym for the index past the
+      end.
+
+    @param[in] ptr  a JSON pointer
+
+    @return reference to the element pointed to by @a ptr
+
+    @complexity Constant.
+
+    @throw std::out_of_range      if the JSON pointer can not be resolved
+    @throw std::domain_error      if an array index begins with '0'
+    @throw std::invalid_argument  if an array index was not a number
+
+    @liveexample{The behavior is shown in the example.,operatorjson_pointer}
+
+    @since version 2.0.0
+    */
+    reference operator[](const json_pointer& ptr)
+    {
+        return ptr.get_unchecked(this);
+    }
+
+    /*!
+    @brief access specified element via JSON Pointer
+
+    Uses a JSON pointer to retrieve a reference to the respective JSON value.
+    No bound checking is performed. The function does not change the JSON
+    value; no `null` values are created. In particular, the the special value
+    `-` yields an exception.
+
+    @param[in] ptr  JSON pointer to the desired element
+
+    @return const reference to the element pointed to by @a ptr
+
+    @complexity Constant.
+
+    @throw std::out_of_range      if the JSON pointer can not be resolved
+    @throw std::domain_error      if an array index begins with '0'
+    @throw std::invalid_argument  if an array index was not a number
+
+    @liveexample{The behavior is shown in the example.,operatorjson_pointer_const}
+
+    @since version 2.0.0
+    */
+    const_reference operator[](const json_pointer& ptr) const
+    {
+        return ptr.get_unchecked(this);
+    }
+
+    /*!
+    @brief access specified element via JSON Pointer
+
+    Returns a reference to the element at with specified JSON pointer @a ptr,
+    with bounds checking.
+
+    @param[in] ptr  JSON pointer to the desired element
+
+    @return reference to the element pointed to by @a ptr
+
+    @complexity Constant.
+
+    @throw std::out_of_range      if the JSON pointer can not be resolved
+    @throw std::domain_error      if an array index begins with '0'
+    @throw std::invalid_argument  if an array index was not a number
+
+    @liveexample{The behavior is shown in the example.,at_json_pointer}
+
+    @since version 2.0.0
+    */
+    reference at(const json_pointer& ptr)
+    {
+        return ptr.get_checked(this);
+    }
+
+    /*!
+    @brief access specified element via JSON Pointer
+
+    Returns a const reference to the element at with specified JSON pointer @a
+    ptr, with bounds checking.
+
+    @param[in] ptr  JSON pointer to the desired element
+
+    @return reference to the element pointed to by @a ptr
+
+    @complexity Constant.
+
+    @throw std::out_of_range      if the JSON pointer can not be resolved
+    @throw std::domain_error      if an array index begins with '0'
+    @throw std::invalid_argument  if an array index was not a number
+
+    @liveexample{The behavior is shown in the example.,at_json_pointer_const}
+
+    @since version 2.0.0
+    */
+    const_reference at(const json_pointer& ptr) const
+    {
+        return ptr.get_checked(this);
+    }
+
+    /*!
+    @brief return flattened JSON value
+
+    The function creates a JSON object whose keys are JSON pointers (see [RFC
+    6901](https://tools.ietf.org/html/rfc6901)) and whose values are all
+    primitive. The original JSON value can be restored using the @ref
+    unflatten() function.
+
+    @return an object that maps JSON pointers to primitve values
+
+    @note Empty objects and arrays are flattened to `null` and will not be
+          reconstructed correctly by the @ref unflatten() function.
+
+    @complexity Linear in the size the JSON value.
+
+    @liveexample{The following code shows how a JSON object is flattened to an
+    object whose keys consist of JSON pointers.,flatten}
+
+    @sa @ref unflatten() for the reverse function
+
+    @since version 2.0.0
+    */
+    basic_json flatten() const
+    {
+        basic_json result(value_t::object);
+        json_pointer::flatten("", *this, result);
+        return result;
+    }
+
+    /*!
+    @brief unflatten a previously flattened JSON value
+
+    The function restores the arbitrary nesting of a JSON value that has been
+    flattened before using the @ref flatten() function. The JSON value must
+    meet certain constraints:
+    1. The value must be an object.
+    2. The keys must be JSON pointers (see
+       [RFC 6901](https://tools.ietf.org/html/rfc6901))
+    3. The mapped values must be primitive JSON types.
+
+    @return the original JSON from a flattened version
+
+    @note Empty objects and arrays are flattened by @ref flatten() to `null`
+          values and can not unflattened to their original type. Apart from
+          this example, for a JSON value `j`, the following is always true:
+          `j == j.flatten().unflatten()`.
+
+    @complexity Linear in the size the JSON value.
+
+    @liveexample{The following code shows how a flattened JSON object is
+    unflattened into the original nested JSON object.,unflatten}
+
+    @sa @ref flatten() for the reverse function
+
+    @since version 2.0.0
+    */
+    basic_json unflatten() const
+    {
+        return json_pointer::unflatten(*this);
+    }
+
+    /// @}
+
+    //////////////////////////
+    // JSON Patch functions //
+    //////////////////////////
+
+    /// @name JSON Patch functions
+    /// @{
+
+    /*!
+    @brief applies a JSON patch
+
+    [JSON Patch](http://jsonpatch.com) defines a JSON document structure for
+    expressing a sequence of operations to apply to a JSON) document. With
+    this funcion, a JSON Patch is applied to the current JSON value by
+    executing all operations from the patch.
+
+    @param[in] json_patch  JSON patch document
+    @return patched document
+
+    @note The application of a patch is atomic: Either all operations succeed
+          and the patched document is returned or an exception is thrown. In
+          any case, the original value is not changed: the patch is applied
+          to a copy of the value.
+
+    @throw std::out_of_range if a JSON pointer inside the patch could not
+    be resolved successfully in the current JSON value; example: `"key baz
+    not found"`
+    @throw invalid_argument if the JSON patch is malformed (e.g., mandatory
+    attributes are missing); example: `"operation add must have member path"`
+
+    @complexity Linear in the size of the JSON value and the length of the
+    JSON patch. As usually only a fraction of the JSON value is affected by
+    the patch, the complexity can usually be neglected.
+
+    @liveexample{The following code shows how a JSON patch is applied to a
+    value.,patch}
+
+    @sa @ref diff -- create a JSON patch by comparing two JSON values
+
+    @sa [RFC 6902 (JSON Patch)](https://tools.ietf.org/html/rfc6902)
+    @sa [RFC 6901 (JSON Pointer)](https://tools.ietf.org/html/rfc6901)
+
+    @since version 2.0.0
+    */
+    basic_json patch(const basic_json& json_patch) const
+    {
+        // make a working copy to apply the patch to
+        basic_json result = *this;
+
+        // the valid JSON Patch operations
+        enum class patch_operations {add, remove, replace, move, copy, test, invalid};
+
+        const auto get_op = [](const std::string op)
+        {
+            if (op == "add")
+            {
+                return patch_operations::add;
+            }
+            if (op == "remove")
+            {
+                return patch_operations::remove;
+            }
+            if (op == "replace")
+            {
+                return patch_operations::replace;
+            }
+            if (op == "move")
+            {
+                return patch_operations::move;
+            }
+            if (op == "copy")
+            {
+                return patch_operations::copy;
+            }
+            if (op == "test")
+            {
+                return patch_operations::test;
+            }
+
+            return patch_operations::invalid;
+        };
+
+        // wrapper for "add" operation; add value at ptr
+        const auto operation_add = [&result](json_pointer & ptr, basic_json val)
+        {
+            // adding to the root of the target document means replacing it
+            if (ptr.is_root())
+            {
+                result = val;
+            }
+            else
+            {
+                // make sure the top element of the pointer exists
+                json_pointer top_pointer = ptr.top();
+                if (top_pointer != ptr)
+                {
+                    result.at(top_pointer);
+                }
+
+                // get reference to parent of JSON pointer ptr
+                const auto last_path = ptr.pop_back();
+                basic_json& parent = result[ptr];
+
+                switch (parent.m_type)
+                {
+                    case value_t::null:
+                    case value_t::object:
+                    {
+                        // use operator[] to add value
+                        parent[last_path] = val;
+                        break;
+                    }
+
+                    case value_t::array:
+                    {
+                        if (last_path == "-")
+                        {
+                            // special case: append to back
+                            parent.push_back(val);
+                        }
+                        else
+                        {
+                            const auto idx = std::stoi(last_path);
+                            if (static_cast<size_type>(idx) > parent.size())
+                            {
+                                // avoid undefined behavior
+                                throw std::out_of_range("array index " + std::to_string(idx) + " is out of range");
+                            }
+                            else
+                            {
+                                // default case: insert add offset
+                                parent.insert(parent.begin() + static_cast<difference_type>(idx), val);
+                            }
+                        }
+                        break;
+                    }
+
+                    default:
+                    {
+                        // if there exists a parent it cannot be primitive
+                        assert(false);  // LCOV_EXCL_LINE
+                    }
+                }
+            }
+        };
+
+        // wrapper for "remove" operation; remove value at ptr
+        const auto operation_remove = [&result](json_pointer & ptr)
+        {
+            // get reference to parent of JSON pointer ptr
+            const auto last_path = ptr.pop_back();
+            basic_json& parent = result.at(ptr);
+
+            // remove child
+            if (parent.is_object())
+            {
+                // perform range check
+                auto it = parent.find(last_path);
+                if (it != parent.end())
+                {
+                    parent.erase(it);
+                }
+                else
+                {
+                    throw std::out_of_range("key '" + last_path + "' not found");
+                }
+            }
+            else if (parent.is_array())
+            {
+                // note erase performs range check
+                parent.erase(static_cast<size_type>(std::stoi(last_path)));
+            }
+        };
+
+        // type check
+        if (not json_patch.is_array())
+        {
+            // a JSON patch must be an array of objects
+            throw std::invalid_argument("JSON patch must be an array of objects");
+        }
+
+        // iterate and apply th eoperations
+        for (const auto& val : json_patch)
+        {
+            // wrapper to get a value for an operation
+            const auto get_value = [&val](const std::string & op,
+                                          const std::string & member,
+                                          bool string_type) -> basic_json&
+            {
+                // find value
+                auto it = val.m_value.object->find(member);
+
+                // context-sensitive error message
+                const auto error_msg = (op == "op") ? "operation" : "operation '" + op + "'";
+
+                // check if desired value is present
+                if (it == val.m_value.object->end())
+                {
+                    throw std::invalid_argument(error_msg + " must have member '" + member + "'");
+                }
+
+                // check if result is of type string
+                if (string_type and not it->second.is_string())
+                {
+                    throw std::invalid_argument(error_msg + " must have string member '" + member + "'");
+                }
+
+                // no error: return value
+                return it->second;
+            };
+
+            // type check
+            if (not val.is_object())
+            {
+                throw std::invalid_argument("JSON patch must be an array of objects");
+            }
+
+            // collect mandatory members
+            const std::string op = get_value("op", "op", true);
+            const std::string path = get_value(op, "path", true);
+            json_pointer ptr(path);
+
+            switch (get_op(op))
+            {
+                case patch_operations::add:
+                {
+                    operation_add(ptr, get_value("add", "value", false));
+                    break;
+                }
+
+                case patch_operations::remove:
+                {
+                    operation_remove(ptr);
+                    break;
+                }
+
+                case patch_operations::replace:
+                {
+                    // the "path" location must exist - use at()
+                    result.at(ptr) = get_value("replace", "value", false);
+                    break;
+                }
+
+                case patch_operations::move:
+                {
+                    const std::string from_path = get_value("move", "from", true);
+                    json_pointer from_ptr(from_path);
+
+                    // the "from" location must exist - use at()
+                    basic_json v = result.at(from_ptr);
+
+                    // The move operation is functionally identical to a
+                    // "remove" operation on the "from" location, followed
+                    // immediately by an "add" operation at the target
+                    // location with the value that was just removed.
+                    operation_remove(from_ptr);
+                    operation_add(ptr, v);
+                    break;
+                }
+
+                case patch_operations::copy:
+                {
+                    const std::string from_path = get_value("copy", "from", true);;
+                    const json_pointer from_ptr(from_path);
+
+                    // the "from" location must exist - use at()
+                    result[ptr] = result.at(from_ptr);
+                    break;
+                }
+
+                case patch_operations::test:
+                {
+                    bool success = false;
+                    try
+                    {
+                        // check if "value" matches the one at "path"
+                        // the "path" location must exist - use at()
+                        success = (result.at(ptr) == get_value("test", "value", false));
+                    }
+                    catch (std::out_of_range&)
+                    {
+                        // ignore out of range errors: success remains false
+                    }
+
+                    // throw an exception if test fails
+                    if (not success)
+                    {
+                        throw std::domain_error("unsuccessful: " + val.dump());
+                    }
+
+                    break;
+                }
+
+                case patch_operations::invalid:
+                {
+                    // op must be "add", "remove", "replace", "move", "copy", or
+                    // "test"
+                    throw std::invalid_argument("operation value '" + op + "' is invalid");
+                }
+            }
+        }
+
+        return result;
+    }
+
+    /*!
+    @brief creates a diff as a JSON patch
+
+    Creates a [JSON Patch](http://jsonpatch.com) so that value @a source can
+    be changed into the value @a target by calling @ref patch function.
+
+    @invariant For two JSON values @a source and @a target, the following code
+    yields always `true`:
+    @code {.cpp}
+    source.patch(diff(source, target)) == target;
+    @endcode
+
+    @note Currently, only `remove`, `add`, and `replace` operations are
+          generated.
+
+    @param[in] source  JSON value to copare from
+    @param[in] target  JSON value to copare against
+    @param[in] path    helper value to create JSON pointers
+
+    @return a JSON patch to convert the @a source to @a target
+
+    @complexity Linear in the lengths of @a source and @a target.
+
+    @liveexample{The following code shows how a JSON patch is created as a
+    diff for two JSON values.,diff}
+
+    @sa @ref patch -- apply a JSON patch
+
+    @sa [RFC 6902 (JSON Patch)](https://tools.ietf.org/html/rfc6902)
+
+    @since version 2.0.0
+    */
+    static basic_json diff(const basic_json& source,
+                           const basic_json& target,
+                           const std::string& path = "")
+    {
+        // the patch
+        basic_json result(value_t::array);
+
+        // if the values are the same, return empty patch
+        if (source == target)
+        {
+            return result;
+        }
+
+        if (source.type() != target.type())
+        {
+            // different types: replace value
+            result.push_back(
+            {
+                {"op", "replace"},
+                {"path", path},
+                {"value", target}
+            });
+        }
+        else
+        {
+            switch (source.type())
+            {
+                case value_t::array:
+                {
+                    // first pass: traverse common elements
+                    size_t i = 0;
+                    while (i < source.size() and i < target.size())
+                    {
+                        // recursive call to compare array values at index i
+                        auto temp_diff = diff(source[i], target[i], path + "/" + std::to_string(i));
+                        result.insert(result.end(), temp_diff.begin(), temp_diff.end());
+                        ++i;
+                    }
+
+                    // i now reached the end of at least one array
+                    // in a second pass, traverse the remaining elements
+
+                    // remove my remaining elements
+                    const auto end_index = static_cast<difference_type>(result.size());
+                    while (i < source.size())
+                    {
+                        // add operations in reverse order to avoid invalid
+                        // indices
+                        result.insert(result.begin() + end_index, object(
+                        {
+                            {"op", "remove"},
+                            {"path", path + "/" + std::to_string(i)}
+                        }));
+                        ++i;
+                    }
+
+                    // add other remaining elements
+                    while (i < target.size())
+                    {
+                        result.push_back(
+                        {
+                            {"op", "add"},
+                            {"path", path + "/" + std::to_string(i)},
+                            {"value", target[i]}
+                        });
+                        ++i;
+                    }
+
+                    break;
+                }
+
+                case value_t::object:
+                {
+                    // first pass: traverse this object's elements
+                    for (auto it = source.begin(); it != source.end(); ++it)
+                    {
+                        // escape the key name to be used in a JSON patch
+                        const auto key = json_pointer::escape(it.key());
+
+                        if (target.find(it.key()) != target.end())
+                        {
+                            // recursive call to compare object values at key it
+                            auto temp_diff = diff(it.value(), target[it.key()], path + "/" + key);
+                            result.insert(result.end(), temp_diff.begin(), temp_diff.end());
+                        }
+                        else
+                        {
+                            // found a key that is not in o -> remove it
+                            result.push_back(object(
+                            {
+                                {"op", "remove"},
+                                {"path", path + "/" + key}
+                            }));
+                        }
+                    }
+
+                    // second pass: traverse other object's elements
+                    for (auto it = target.begin(); it != target.end(); ++it)
+                    {
+                        if (source.find(it.key()) == source.end())
+                        {
+                            // found a key that is not in this -> add it
+                            const auto key = json_pointer::escape(it.key());
+                            result.push_back(
+                            {
+                                {"op", "add"},
+                                {"path", path + "/" + key},
+                                {"value", it.value()}
+                            });
+                        }
+                    }
+
+                    break;
+                }
+
+                default:
+                {
+                    // both primitive type: replace value
+                    result.push_back(
+                    {
+                        {"op", "replace"},
+                        {"path", path},
+                        {"value", target}
+                    });
+                    break;
+                }
+            }
+        }
+
+        return result;
+    }
+
+    /// @}
+};
+
+
+/////////////
+// presets //
+/////////////
+
+/*!
+@brief default JSON class
+
+This type is the default specialization of the @ref basic_json class which
+uses the standard template types.
+
+@since version 1.0.0
+*/
+using json = basic_json<>;
+}
+
+
+///////////////////////
+// nonmember support //
+///////////////////////
+
+// specialization of std::swap, and std::hash
+namespace std
+{
+/*!
+@brief exchanges the values of two JSON objects
+
+@since version 1.0.0
+*/
+template<>
+inline void swap(nlohmann::json& j1,
+                 nlohmann::json& j2) noexcept(
+                     is_nothrow_move_constructible<nlohmann::json>::value and
+                     is_nothrow_move_assignable<nlohmann::json>::value
+                 )
+{
+    j1.swap(j2);
+}
+
+/// hash value for JSON objects
+template<>
+struct hash<nlohmann::json>
+{
+    /*!
+    @brief return a hash value for a JSON object
+
+    @since version 1.0.0
+    */
+    std::size_t operator()(const nlohmann::json& j) const
+    {
+        // a naive hashing via the string representation
+        const auto& h = hash<nlohmann::json::string_t>();
+        return h(j.dump());
+    }
+};
+}
+
+/*!
+@brief user-defined string literal for JSON values
+
+This operator implements a user-defined string literal for JSON objects. It
+can be used by adding `"_json"` to a string literal and returns a JSON object
+if no parse error occurred.
+
+@param[in] s  a string representation of a JSON object
+@param[in] n  the length of string @a s
+@return a JSON object
+
+@since version 1.0.0
+*/
+inline nlohmann::json operator "" _json(const char* s, std::size_t n)
+{
+    return nlohmann::json::parse(s, s + n);
+}
+
+/*!
+@brief user-defined string literal for JSON pointer
+
+This operator implements a user-defined string literal for JSON Pointers. It
+can be used by adding `"_json_pointer"` to a string literal and returns a JSON pointer
+object if no parse error occurred.
+
+@param[in] s  a string representation of a JSON Pointer
+@param[in] n  the length of string @a s
+@return a JSON pointer object
+
+@since version 2.0.0
+*/
+inline nlohmann::json::json_pointer operator "" _json_pointer(const char* s, std::size_t n)
+{
+    return nlohmann::json::json_pointer(std::string(s, n));
+}
+
+// restore GCC/clang diagnostic settings
+#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
+    #pragma GCC diagnostic pop
+#endif
+
+#endif