diff --git a/include/nlohmann/detail/meta/cpp_future.hpp b/include/nlohmann/detail/meta/cpp_future.hpp index dd929ee142..4ba1a55714 100644 --- a/include/nlohmann/detail/meta/cpp_future.hpp +++ b/include/nlohmann/detail/meta/cpp_future.hpp @@ -2,19 +2,32 @@ #include // size_t #include // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type +#include // index_sequence, make_index_sequence, index_sequence_for + +#include namespace nlohmann { namespace detail { -// alias templates to reduce boilerplate -template -using enable_if_t = typename std::enable_if::type; template using uncvref_t = typename std::remove_cv::type>::type; -// implementation of C++14 index_sequence and affiliates +#ifdef JSON_HAS_CPP_14 + +// the following utilities are natively available in C++14 +using std::enable_if_t; +using std::index_sequence; +using std::make_index_sequence; +using std::index_sequence_for; + +#else + +// alias templates to reduce boilerplate +template +using enable_if_t = typename std::enable_if::type; + // source: https://stackoverflow.com/a/32223343 template struct index_sequence @@ -45,6 +58,8 @@ template<> struct make_index_sequence<1> : index_sequence<0> {}; template using index_sequence_for = make_index_sequence; +#endif + // dispatch utility (taken from ranges-v3) template struct priority_tag : priority_tag < N - 1 > {}; template<> struct priority_tag<0> {}; @@ -58,5 +73,6 @@ struct static_const template constexpr T static_const::value; + } // namespace detail } // namespace nlohmann diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp index 09498b621c..88c8fa74d9 100644 --- a/single_include/nlohmann/json.hpp +++ b/single_include/nlohmann/json.hpp @@ -2736,19 +2736,33 @@ class other_error : public exception #include // size_t #include // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type +#include // index_sequence, make_index_sequence, index_sequence_for + +// #include + namespace nlohmann { namespace detail { -// alias templates to reduce boilerplate -template -using enable_if_t = typename std::enable_if::type; template using uncvref_t = typename std::remove_cv::type>::type; -// implementation of C++14 index_sequence and affiliates +#ifdef JSON_HAS_CPP_14 + +// the following utilities are natively available in C++14 +using std::enable_if_t; +using std::index_sequence; +using std::make_index_sequence; +using std::index_sequence_for; + +#else + +// alias templates to reduce boilerplate +template +using enable_if_t = typename std::enable_if::type; + // source: https://stackoverflow.com/a/32223343 template struct index_sequence @@ -2779,6 +2793,8 @@ template<> struct make_index_sequence<1> : index_sequence<0> {}; template using index_sequence_for = make_index_sequence; +#endif + // dispatch utility (taken from ranges-v3) template struct priority_tag : priority_tag < N - 1 > {}; template<> struct priority_tag<0> {}; @@ -2792,6 +2808,7 @@ struct static_const template constexpr T static_const::value; + } // namespace detail } // namespace nlohmann