Merge pull request #1342 from davedissian/bugfix/sfinae-iterator-traits
Add a SFINAE friendly iterator_traits and use that instead.
This commit is contained in:
commit
4f270e38cc
5 changed files with 125 additions and 20 deletions
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@ -360,7 +360,7 @@ class input_adapter
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/// input adapter for iterator range with contiguous storage
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/// input adapter for iterator range with contiguous storage
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template<class IteratorType,
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template<class IteratorType,
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typename std::enable_if<
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typename std::enable_if<
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std::is_same<typename std::iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
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std::is_same<typename iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
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int>::type = 0>
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int>::type = 0>
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input_adapter(IteratorType first, IteratorType last)
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input_adapter(IteratorType first, IteratorType last)
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{
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{
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@ -379,7 +379,7 @@ class input_adapter
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// assertion to check that each element is 1 byte long
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// assertion to check that each element is 1 byte long
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static_assert(
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static_assert(
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sizeof(typename std::iterator_traits<IteratorType>::value_type) == 1,
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sizeof(typename iterator_traits<IteratorType>::value_type) == 1,
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"each element in the iterator range must have the size of 1 byte");
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"each element in the iterator range must have the size of 1 byte");
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const auto len = static_cast<size_t>(std::distance(first, last));
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const auto len = static_cast<size_t>(std::distance(first, last));
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@ -403,7 +403,7 @@ class input_adapter
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/// input adapter for contiguous container
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/// input adapter for contiguous container
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template<class ContiguousContainer, typename
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template<class ContiguousContainer, typename
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std::enable_if<not std::is_pointer<ContiguousContainer>::value and
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std::enable_if<not std::is_pointer<ContiguousContainer>::value and
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std::is_base_of<std::random_access_iterator_tag, typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
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std::is_base_of<std::random_access_iterator_tag, typename iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
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int>::type = 0>
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int>::type = 0>
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input_adapter(const ContiguousContainer& c)
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input_adapter(const ContiguousContainer& c)
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: input_adapter(std::begin(c), std::end(c)) {}
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: input_adapter(std::begin(c), std::end(c)) {}
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49
include/nlohmann/detail/iterators/iterator_traits.hpp
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49
include/nlohmann/detail/iterators/iterator_traits.hpp
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@ -0,0 +1,49 @@
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#pragma once
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#include <iterator> // random_access_iterator_tag
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#include <nlohmann/detail/meta/void_t.hpp>
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#include <nlohmann/detail/meta/cpp_future.hpp>
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namespace nlohmann
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{
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namespace detail
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{
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template <typename It, typename = void>
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struct iterator_types {};
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template <typename It>
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struct iterator_types<
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It,
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void_t<typename It::difference_type, typename It::value_type, typename It::pointer,
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typename It::reference, typename It::iterator_category>> {
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using difference_type = typename It::difference_type;
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using value_type = typename It::value_type;
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using pointer = typename It::pointer;
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using reference = typename It::reference;
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using iterator_category = typename It::iterator_category;
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};
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// This is required as some compilers implement std::iterator_traits in a way that
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// doesn't work with SFINAE. See https://github.com/nlohmann/json/issues/1341.
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template <typename T, typename = void>
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struct iterator_traits
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{
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};
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template <typename T>
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struct iterator_traits<T, enable_if_t<!std::is_pointer<T>::value>>
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: iterator_types<T>
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{
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};
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template <typename T>
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struct iterator_traits<T*, enable_if_t<std::is_object<T>::value>> {
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using iterator_category = std::random_access_iterator_tag;
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using value_type = T;
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using difference_type = ptrdiff_t;
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using pointer = T*;
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using reference = T&;
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};
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}
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}
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@ -6,6 +6,7 @@
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#include <utility> // declval
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#include <utility> // declval
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#include <nlohmann/json_fwd.hpp>
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#include <nlohmann/json_fwd.hpp>
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#include <nlohmann/detail/iterators/iterator_traits.hpp>
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#include <nlohmann/detail/meta/cpp_future.hpp>
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#include <nlohmann/detail/meta/cpp_future.hpp>
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#include <nlohmann/detail/meta/detected.hpp>
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#include <nlohmann/detail/meta/detected.hpp>
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#include <nlohmann/detail/macro_scope.hpp>
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#include <nlohmann/detail/macro_scope.hpp>
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@ -131,10 +132,10 @@ template <typename T, typename = void>
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struct is_iterator_traits : std::false_type {};
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struct is_iterator_traits : std::false_type {};
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template <typename T>
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template <typename T>
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struct is_iterator_traits<std::iterator_traits<T>>
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struct is_iterator_traits<iterator_traits<T>>
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{
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{
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private:
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private:
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using traits = std::iterator_traits<T>;
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using traits = iterator_traits<T>;
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public:
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public:
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static constexpr auto value =
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static constexpr auto value =
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@ -251,7 +252,7 @@ struct is_compatible_array_type_impl <
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// Therefore it is detected as a CompatibleArrayType.
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// Therefore it is detected as a CompatibleArrayType.
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// The real fix would be to have an Iterable concept.
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// The real fix would be to have an Iterable concept.
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not is_iterator_traits<
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not is_iterator_traits<
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std::iterator_traits<CompatibleArrayType>>::value >>
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iterator_traits<CompatibleArrayType>>::value >>
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{
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{
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static constexpr bool value =
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static constexpr bool value =
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std::is_constructible<BasicJsonType,
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std::is_constructible<BasicJsonType,
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@ -288,7 +289,7 @@ struct is_constructible_array_type_impl <
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// Therefore it is detected as a ConstructibleArrayType.
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// Therefore it is detected as a ConstructibleArrayType.
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// The real fix would be to have an Iterable concept.
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// The real fix would be to have an Iterable concept.
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not is_iterator_traits <
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not is_iterator_traits <
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std::iterator_traits<ConstructibleArrayType >>::value and
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iterator_traits<ConstructibleArrayType >>::value and
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(std::is_same<typename ConstructibleArrayType::value_type, typename BasicJsonType::array_t::value_type>::value or
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(std::is_same<typename ConstructibleArrayType::value_type, typename BasicJsonType::array_t::value_type>::value or
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has_from_json<BasicJsonType,
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has_from_json<BasicJsonType,
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@ -41,7 +41,7 @@ SOFTWARE.
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#include <functional> // hash, less
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#include <functional> // hash, less
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#include <initializer_list> // initializer_list
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#include <initializer_list> // initializer_list
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#include <iosfwd> // istream, ostream
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#include <iosfwd> // istream, ostream
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#include <iterator> // iterator_traits, random_access_iterator_tag
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#include <iterator> // random_access_iterator_tag
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#include <numeric> // accumulate
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#include <numeric> // accumulate
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#include <string> // string, stoi, to_string
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#include <string> // string, stoi, to_string
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#include <utility> // declval, forward, move, pair, swap
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#include <utility> // declval, forward, move, pair, swap
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@ -41,7 +41,7 @@ SOFTWARE.
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#include <functional> // hash, less
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#include <functional> // hash, less
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#include <initializer_list> // initializer_list
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#include <initializer_list> // initializer_list
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#include <iosfwd> // istream, ostream
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#include <iosfwd> // istream, ostream
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#include <iterator> // iterator_traits, random_access_iterator_tag
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#include <iterator> // random_access_iterator_tag
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#include <numeric> // accumulate
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#include <numeric> // accumulate
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#include <string> // string, stoi, to_string
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#include <string> // string, stoi, to_string
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#include <utility> // declval, forward, move, pair, swap
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#include <utility> // declval, forward, move, pair, swap
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@ -324,12 +324,10 @@ constexpr T static_const<T>::value;
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// #include <nlohmann/json_fwd.hpp>
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// #include <nlohmann/json_fwd.hpp>
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// #include <nlohmann/detail/meta/cpp_future.hpp>
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// #include <nlohmann/detail/iterators/iterator_traits.hpp>
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// #include <nlohmann/detail/meta/detected.hpp>
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#include <type_traits>
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#include <iterator> // random_access_iterator_tag
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// #include <nlohmann/detail/meta/void_t.hpp>
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// #include <nlohmann/detail/meta/void_t.hpp>
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@ -346,6 +344,63 @@ template <typename ...Ts> using void_t = typename make_void<Ts...>::type;
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} // namespace detail
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} // namespace detail
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} // namespace nlohmann
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} // namespace nlohmann
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// #include <nlohmann/detail/meta/cpp_future.hpp>
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namespace nlohmann
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{
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namespace detail
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{
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template <typename It, typename = void>
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struct iterator_types {};
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template <typename It>
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struct iterator_types <
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It,
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void_t<typename It::difference_type, typename It::value_type, typename It::pointer,
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typename It::reference, typename It::iterator_category >>
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{
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using difference_type = typename It::difference_type;
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using value_type = typename It::value_type;
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using pointer = typename It::pointer;
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using reference = typename It::reference;
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using iterator_category = typename It::iterator_category;
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};
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// This is required as some compilers implement std::iterator_traits in a way that
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// doesn't work with SFINAE. See https://github.com/nlohmann/json/issues/1341.
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template <typename T, typename = void>
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struct iterator_traits
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{
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};
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template <typename T>
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struct iterator_traits < T, enable_if_t < !std::is_pointer<T>::value >>
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: iterator_types<T>
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{
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};
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template <typename T>
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struct iterator_traits<T*, enable_if_t<std::is_object<T>::value>>
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{
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using iterator_category = std::random_access_iterator_tag;
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using value_type = T;
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using difference_type = ptrdiff_t;
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using pointer = T*;
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using reference = T&;
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};
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}
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}
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// #include <nlohmann/detail/meta/cpp_future.hpp>
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// #include <nlohmann/detail/meta/detected.hpp>
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#include <type_traits>
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// #include <nlohmann/detail/meta/void_t.hpp>
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// http://en.cppreference.com/w/cpp/experimental/is_detected
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// http://en.cppreference.com/w/cpp/experimental/is_detected
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namespace nlohmann
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namespace nlohmann
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@ -522,10 +577,10 @@ template <typename T, typename = void>
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struct is_iterator_traits : std::false_type {};
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struct is_iterator_traits : std::false_type {};
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template <typename T>
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template <typename T>
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struct is_iterator_traits<std::iterator_traits<T>>
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struct is_iterator_traits<iterator_traits<T>>
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{
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{
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private:
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private:
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using traits = std::iterator_traits<T>;
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using traits = iterator_traits<T>;
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public:
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public:
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static constexpr auto value =
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static constexpr auto value =
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@ -642,7 +697,7 @@ struct is_compatible_array_type_impl <
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// Therefore it is detected as a CompatibleArrayType.
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// Therefore it is detected as a CompatibleArrayType.
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// The real fix would be to have an Iterable concept.
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// The real fix would be to have an Iterable concept.
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not is_iterator_traits<
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not is_iterator_traits<
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std::iterator_traits<CompatibleArrayType>>::value >>
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iterator_traits<CompatibleArrayType>>::value >>
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{
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{
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static constexpr bool value =
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static constexpr bool value =
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std::is_constructible<BasicJsonType,
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std::is_constructible<BasicJsonType,
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@ -679,7 +734,7 @@ struct is_constructible_array_type_impl <
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// Therefore it is detected as a ConstructibleArrayType.
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// Therefore it is detected as a ConstructibleArrayType.
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// The real fix would be to have an Iterable concept.
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// The real fix would be to have an Iterable concept.
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not is_iterator_traits <
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not is_iterator_traits <
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std::iterator_traits<ConstructibleArrayType >>::value and
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iterator_traits<ConstructibleArrayType >>::value and
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(std::is_same<typename ConstructibleArrayType::value_type, typename BasicJsonType::array_t::value_type>::value or
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(std::is_same<typename ConstructibleArrayType::value_type, typename BasicJsonType::array_t::value_type>::value or
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has_from_json<BasicJsonType,
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has_from_json<BasicJsonType,
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@ -2409,7 +2464,7 @@ class input_adapter
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/// input adapter for iterator range with contiguous storage
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/// input adapter for iterator range with contiguous storage
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template<class IteratorType,
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template<class IteratorType,
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typename std::enable_if<
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typename std::enable_if<
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std::is_same<typename std::iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
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std::is_same<typename iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
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int>::type = 0>
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int>::type = 0>
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input_adapter(IteratorType first, IteratorType last)
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input_adapter(IteratorType first, IteratorType last)
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{
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{
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@ -2428,7 +2483,7 @@ class input_adapter
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// assertion to check that each element is 1 byte long
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// assertion to check that each element is 1 byte long
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static_assert(
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static_assert(
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sizeof(typename std::iterator_traits<IteratorType>::value_type) == 1,
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sizeof(typename iterator_traits<IteratorType>::value_type) == 1,
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"each element in the iterator range must have the size of 1 byte");
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"each element in the iterator range must have the size of 1 byte");
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const auto len = static_cast<size_t>(std::distance(first, last));
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const auto len = static_cast<size_t>(std::distance(first, last));
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@ -2452,7 +2507,7 @@ class input_adapter
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/// input adapter for contiguous container
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/// input adapter for contiguous container
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template<class ContiguousContainer, typename
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template<class ContiguousContainer, typename
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std::enable_if<not std::is_pointer<ContiguousContainer>::value and
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std::enable_if<not std::is_pointer<ContiguousContainer>::value and
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std::is_base_of<std::random_access_iterator_tag, typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
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std::is_base_of<std::random_access_iterator_tag, typename iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
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int>::type = 0>
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int>::type = 0>
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input_adapter(const ContiguousContainer& c)
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input_adapter(const ContiguousContainer& c)
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: input_adapter(std::begin(c), std::end(c)) {}
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: input_adapter(std::begin(c), std::end(c)) {}
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