// -*- C++ -*- //===----------------------------------------------------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// #ifndef _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H #define _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H #include <__concepts/arithmetic.h> #include <__config> #include <__type_traits/conditional.h> #include <__type_traits/is_object.h> #include <__type_traits/is_primary_template.h> #include <__type_traits/make_signed.h> #include <__type_traits/remove_cvref.h> #include <__utility/declval.h> #include <cstddef> #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) # pragma GCC system_header #endif _LIBCPP_BEGIN_NAMESPACE_STD #if _LIBCPP_STD_VER >= 20 // [incrementable.traits] template <class> struct incrementable_traits {}; template <class _Tp> requires is_object_v<_Tp> struct incrementable_traits<_Tp*> { using difference_type = ptrdiff_t; }; template <class _Ip> struct incrementable_traits<const _Ip> : incrementable_traits<_Ip> {}; template <class _Tp> concept __has_member_difference_type = requires { typename _Tp::difference_type; }; template <__has_member_difference_type _Tp> struct incrementable_traits<_Tp> { using difference_type = typename _Tp::difference_type; }; template <class _Tp> concept __has_integral_minus = requires(const _Tp& __x, const _Tp& __y) { { __x - __y } -> integral; }; template <__has_integral_minus _Tp> requires(!__has_member_difference_type<_Tp>) struct incrementable_traits<_Tp> { using difference_type = make_signed_t<decltype(std::declval<_Tp>() - std::declval<_Tp>())>; }; template <class> struct iterator_traits; // Let `RI` be `remove_cvref_t<I>`. The type `iter_difference_t<I>` denotes // `incrementable_traits<RI>::difference_type` if `iterator_traits<RI>` names a specialization // generated from the primary template, and `iterator_traits<RI>::difference_type` otherwise. template <class _Ip> using iter_difference_t = typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value, incrementable_traits<remove_cvref_t<_Ip> >, iterator_traits<remove_cvref_t<_Ip> > >::difference_type; #endif // _LIBCPP_STD_VER >= 20 _LIBCPP_END_NAMESPACE_STD #endif // _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H