__cxx03/__iterator/readable_traits.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___CXX03___ITERATOR_READABLE_TRAITS_H
0011 #define _LIBCPP___CXX03___ITERATOR_READABLE_TRAITS_H
0012
0013 #include <__cxx03/__concepts/same_as.h>
0014 #include <__cxx03/__config>
0015 #include <__cxx03/__type_traits/conditional.h>
0016 #include <__cxx03/__type_traits/is_array.h>
0017 #include <__cxx03/__type_traits/is_object.h>
0018 #include <__cxx03/__type_traits/is_primary_template.h>
0019 #include <__cxx03/__type_traits/remove_cv.h>
0020 #include <__cxx03/__type_traits/remove_cvref.h>
0021 #include <__cxx03/__type_traits/remove_extent.h>
0022
0023 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0024 #  pragma GCC system_header
0025 #endif
0026
0027 _LIBCPP_BEGIN_NAMESPACE_STD
0028
0029 #if _LIBCPP_STD_VER >= 20
0030
0031 // [readable.traits]
0032 template <class>
0033 struct __cond_value_type {};
0034
0035 template <class _Tp>
0036   requires is_object_v<_Tp>
0037 struct __cond_value_type<_Tp> {
0038   using value_type = remove_cv_t<_Tp>;
0039 };
0040
0041 template <class _Tp>
0042 concept __has_member_value_type = requires { typename _Tp::value_type; };
0043
0044 template <class _Tp>
0045 concept __has_member_element_type = requires { typename _Tp::element_type; };
0046
0047 template <class>
0048 struct indirectly_readable_traits {};
0049
0050 template <class _Ip>
0051   requires is_array_v<_Ip>
0052 struct indirectly_readable_traits<_Ip> {
0053   using value_type = remove_cv_t<remove_extent_t<_Ip>>;
0054 };
0055
0056 template <class _Ip>
0057 struct indirectly_readable_traits<const _Ip> : indirectly_readable_traits<_Ip> {};
0058
0059 template <class _Tp>
0060 struct indirectly_readable_traits<_Tp*> : __cond_value_type<_Tp> {};
0061
0062 template <__has_member_value_type _Tp>
0063 struct indirectly_readable_traits<_Tp> : __cond_value_type<typename _Tp::value_type> {};
0064
0065 template <__has_member_element_type _Tp>
0066 struct indirectly_readable_traits<_Tp> : __cond_value_type<typename _Tp::element_type> {};
0067
0068 template <__has_member_value_type _Tp>
0069   requires __has_member_element_type<_Tp>
0070 struct indirectly_readable_traits<_Tp> {};
0071
0072 template <__has_member_value_type _Tp>
0073   requires __has_member_element_type<_Tp> &&
0074            same_as<remove_cv_t<typename _Tp::element_type>, remove_cv_t<typename _Tp::value_type>>
0075 struct indirectly_readable_traits<_Tp> : __cond_value_type<typename _Tp::value_type> {};
0076
0077 #endif // _LIBCPP_STD_VER >= 20
0078
0079 _LIBCPP_END_NAMESPACE_STD
0080
0081 #endif // _LIBCPP___CXX03___ITERATOR_READABLE_TRAITS_H