ad2fbea797
This has the benefit of consistent placement for these macros (outside the namespace, not inside it). This, in turn, makes it more obvious that the condition applies to the entire namespace scope. Compile times are also reduced a bit, since the compiler doesn't have to open a namespace just to close it again. This is enforced with a clang-tidy check. As a drive-by this also fixes a few macro comments.
71 lines
2.1 KiB
C++
71 lines
2.1 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___RANGES_EMPTY_H
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#define _LIBCPP___RANGES_EMPTY_H
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#include <__concepts/class_or_enum.h>
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#include <__config>
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#include <__iterator/concepts.h>
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#include <__ranges/access.h>
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#include <__ranges/size.h>
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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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#if _LIBCPP_STD_VER >= 20
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_LIBCPP_BEGIN_NAMESPACE_STD
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// [range.prim.empty]
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namespace ranges {
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namespace __empty {
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template <class _Tp>
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concept __member_empty = requires(_Tp&& __t) { bool(__t.empty()); };
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template <class _Tp>
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concept __can_invoke_size = !__member_empty<_Tp> && requires(_Tp&& __t) { ranges::size(__t); };
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template <class _Tp>
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concept __can_compare_begin_end = !__member_empty<_Tp> && !__can_invoke_size<_Tp> && requires(_Tp&& __t) {
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bool(ranges::begin(__t) == ranges::end(__t));
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{ ranges::begin(__t) } -> forward_iterator;
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};
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struct __fn {
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template <__member_empty _Tp>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(_Tp&& __t) const noexcept(noexcept(bool(__t.empty()))) {
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return bool(__t.empty());
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}
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template <__can_invoke_size _Tp>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(_Tp&& __t) const noexcept(noexcept(ranges::size(__t))) {
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return ranges::size(__t) == 0;
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}
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template <__can_compare_begin_end _Tp>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(_Tp&& __t) const
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noexcept(noexcept(bool(ranges::begin(__t) == ranges::end(__t)))) {
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return ranges::begin(__t) == ranges::end(__t);
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}
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};
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} // namespace __empty
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inline namespace __cpo {
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inline constexpr auto empty = __empty::__fn{};
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} // namespace __cpo
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} // namespace ranges
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_STD_VER >= 20
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#endif // _LIBCPP___RANGES_EMPTY_H
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