73 lines
2.3 KiB
C++
73 lines
2.3 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_INCREMENTABLE_TRAITS_H
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#define _LIBCPP___ITERATOR_INCREMENTABLE_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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// [incrementable.traits]
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template<class> struct incrementable_traits {};
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template<class _Tp>
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requires is_object_v<_Tp>
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struct incrementable_traits<_Tp*> {
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using difference_type = ptrdiff_t;
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};
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template<class _Ip>
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struct incrementable_traits<const _Ip> : incrementable_traits<_Ip> {};
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template<class _Tp>
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concept __has_member_difference_type = requires { typename _Tp::difference_type; };
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template<__has_member_difference_type _Tp>
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struct incrementable_traits<_Tp> {
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using difference_type = typename _Tp::difference_type;
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};
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template<class _Tp>
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concept __has_integral_minus =
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requires(const _Tp& __x, const _Tp& __y) {
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{ __x - __y } -> integral;
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};
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template<__has_integral_minus _Tp>
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requires (!__has_member_difference_type<_Tp>)
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struct incrementable_traits<_Tp> {
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using difference_type = make_signed_t<decltype(declval<_Tp>() - declval<_Tp>())>;
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};
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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_difference_t<I>` denotes
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// `incrementable_traits<RI>::difference_type` if `iterator_traits<RI>` names a specialization
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// generated from the primary template, and `iterator_traits<RI>::difference_type` otherwise.
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template <class _Ip>
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using iter_difference_t = typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value,
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incrementable_traits<remove_cvref_t<_Ip> >,
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iterator_traits<remove_cvref_t<_Ip> > >::difference_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_INCREMENTABLE_TRAITS_H
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