forked from OSchip/llvm-project
87 lines
2.8 KiB
C++
87 lines
2.8 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ITERATOR_READABLE_TRAITS_H
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#define _LIBCPP___ITERATOR_READABLE_TRAITS_H
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#include <__config>
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#include <concepts>
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#include <type_traits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if !defined(_LIBCPP_HAS_NO_CONCEPTS)
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// [readable.traits]
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template<class> struct __cond_value_type {};
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template<class _Tp>
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requires is_object_v<_Tp>
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struct __cond_value_type<_Tp> { using value_type = remove_cv_t<_Tp>; };
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template<class _Tp>
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concept __has_member_value_type = requires { typename _Tp::value_type; };
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template<class _Tp>
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concept __has_member_element_type = requires { typename _Tp::element_type; };
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template<class> struct indirectly_readable_traits {};
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template<class _Ip>
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requires is_array_v<_Ip>
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struct indirectly_readable_traits<_Ip> {
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using value_type = remove_cv_t<remove_extent_t<_Ip>>;
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};
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template<class _Ip>
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struct indirectly_readable_traits<const _Ip> : indirectly_readable_traits<_Ip> {};
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template<class _Tp>
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struct indirectly_readable_traits<_Tp*> : __cond_value_type<_Tp> {};
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template<__has_member_value_type _Tp>
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struct indirectly_readable_traits<_Tp>
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: __cond_value_type<typename _Tp::value_type> {};
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template<__has_member_element_type _Tp>
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struct indirectly_readable_traits<_Tp>
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: __cond_value_type<typename _Tp::element_type> {};
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template<__has_member_value_type _Tp>
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requires __has_member_element_type<_Tp>
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struct indirectly_readable_traits<_Tp> {};
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template<__has_member_value_type _Tp>
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requires __has_member_element_type<_Tp> &&
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same_as<remove_cv_t<typename _Tp::element_type>,
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remove_cv_t<typename _Tp::value_type>>
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struct indirectly_readable_traits<_Tp>
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: __cond_value_type<typename _Tp::value_type> {};
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template <class>
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struct iterator_traits;
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// Let `RI` be `remove_cvref_t<I>`. The type `iter_value_t<I>` denotes
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// `indirectly_readable_traits<RI>::value_type` if `iterator_traits<RI>` names a specialization
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// generated from the primary template, and `iterator_traits<RI>::value_type` otherwise.
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template <class _Ip>
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using iter_value_t = typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value,
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indirectly_readable_traits<remove_cvref_t<_Ip> >,
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iterator_traits<remove_cvref_t<_Ip> > >::value_type;
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#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___ITERATOR_READABLE_TRAITS_H
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