move json_reverse_iterator outside of basic_json

src/json.hpp

@@ -4459,6 +4459,111 @@ template <typename IteratorType> class iteration_proxy
         return iteration_proxy_internal(container.end());
     }
 };
+
+/*!
+@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:
+    using difference_type = std::ptrdiff_t;
+    /// 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 static_cast<json_reverse_iterator>(base_iterator::operator++(1));
+    }
+
+    /// pre-increment (++it)
+    json_reverse_iterator& operator++()
+    {
+        return static_cast<json_reverse_iterator&>(base_iterator::operator++());
+    }
+
+    /// post-decrement (it--)
+    json_reverse_iterator operator--(int)
+    {
+        return static_cast<json_reverse_iterator>(base_iterator::operator--(1));
+    }
+
+    /// pre-decrement (--it)
+    json_reverse_iterator& operator--()
+    {
+        return static_cast<json_reverse_iterator&>(base_iterator::operator--());
+    }
+
+    /// add to iterator
+    json_reverse_iterator& operator+=(difference_type i)
+    {
+        return static_cast<json_reverse_iterator&>(base_iterator::operator+=(i));
+    }
+
+    /// add to iterator
+    json_reverse_iterator operator+(difference_type i) const
+    {
+        return static_cast<json_reverse_iterator>(base_iterator::operator+(i));
+    }
+
+    /// subtract from iterator
+    json_reverse_iterator operator-(difference_type i) const
+    {
+        return static_cast<json_reverse_iterator>(base_iterator::operator-(i));
+    }
+
+    /// return difference
+    difference_type operator-(const json_reverse_iterator& other) const
+    {
+        return base_iterator(*this) - base_iterator(other);
+    }
+
+    /// access to successor
+    reference operator[](difference_type n) const
+    {
+        return *(this->operator+(n));
+    }
+
+    /// return the key of an object iterator
+    auto key() const -> decltype(std::declval<Base>().key())
+    {
+        auto it = --this->base();
+        return it.key();
+    }
+
+    /// return the value of an iterator
+    reference value() const
+    {
+        auto it = --this->base();
+        return it.operator * ();
+    }
+};
 } // namespace detail
 
 /// namespace to hold default `to_json` / `from_json` functions
@@ -4946,11 +5051,11 @@ class basic_json
     using iter_impl = ::nlohmann::detail::iter_impl<BasicJsonType>;
     template <typename Iterator>
     using iteration_proxy = ::nlohmann::detail::iteration_proxy<Iterator>;
+    template<typename Base> using json_reverse_iterator = ::nlohmann::detail::json_reverse_iterator<Base>;
 
   public:
     using value_t = detail::value_t;
     // forward declarations
-    template<typename Base> class json_reverse_iterator;
     using json_pointer = ::nlohmann::json_pointer;
     template<typename T, typename SFINAE>
     using json_serializer = JSONSerializer<T, SFINAE>;
@@ -11298,114 +11403,6 @@ class basic_json
     /// the value of the current element
     json_value m_value = {};
 
-  public:
-    /*!
-    @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 static_cast<json_reverse_iterator>(base_iterator::operator++(1));
-        }
-
-        /// pre-increment (++it)
-        json_reverse_iterator& operator++()
-        {
-            return static_cast<json_reverse_iterator&>(base_iterator::operator++());
-        }
-
-        /// post-decrement (it--)
-        json_reverse_iterator operator--(int)
-        {
-            return static_cast<json_reverse_iterator>(base_iterator::operator--(1));
-        }
-
-        /// pre-decrement (--it)
-        json_reverse_iterator& operator--()
-        {
-            return static_cast<json_reverse_iterator&>(base_iterator::operator--());
-        }
-
-        /// add to iterator
-        json_reverse_iterator& operator+=(difference_type i)
-        {
-            return static_cast<json_reverse_iterator&>(base_iterator::operator+=(i));
-        }
-
-        /// add to iterator
-        json_reverse_iterator operator+(difference_type i) const
-        {
-            return static_cast<json_reverse_iterator>(base_iterator::operator+(i));
-        }
-
-        /// subtract from iterator
-        json_reverse_iterator operator-(difference_type i) const
-        {
-            return static_cast<json_reverse_iterator>(base_iterator::operator-(i));
-        }
-
-        /// return difference
-        difference_type operator-(const json_reverse_iterator& other) const
-        {
-            return base_iterator(*this) - base_iterator(other);
-        }
-
-        /// 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:
     //////////////////////////////////////////
     // binary serialization/deserialization //
     //////////////////////////////////////////