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freebsd
GitHub Repository: freebsd/freebsd-src
 Path: blob/main/contrib/llvm-project/libcxx/include/__iterator/incrementable_traits.h
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// -*- 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 <__concepts/arithmetic.h>

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#include <__config>

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#include <__type_traits/conditional.h>

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#include <__type_traits/is_object.h>

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#include <__type_traits/is_primary_template.h>

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#include <__type_traits/make_signed.h>

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#include <__type_traits/remove_cvref.h>

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#include <__utility/declval.h>

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#include <cstddef>

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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 _LIBCPP_STD_VER >= 20

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// [incrementable.traits]

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template <class>

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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 = 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(std::declval<_Tp>() - std::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 =

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    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 // _LIBCPP_STD_VER >= 20

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_LIBCPP_END_NAMESPACE_STD

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#endif // _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H

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