52 lines
1.6 KiB
C++
52 lines
1.6 KiB
C++
//===----------------------------------------------------------------------===//
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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___ALGORITHM_MAKE_PROJECTED_H
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#define _LIBCPP___ALGORITHM_MAKE_PROJECTED_H
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#include <__concepts/same_as.h>
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#include <__config>
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#include <__functional/identity.h>
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#include <__functional/invoke.h>
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#include <__utility/forward.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 > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
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_LIBCPP_BEGIN_NAMESPACE_STD
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namespace ranges {
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template <class _Comp, class _Proj>
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_LIBCPP_HIDE_FROM_ABI constexpr static
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decltype(auto) __make_projected_comp(_Comp& __comp, _Proj& __proj) {
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if constexpr (same_as<_Proj, identity>) {
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// Avoid creating the lambda and just use the pristine comparator -- for certain algorithms, this would enable
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// optimizations that rely on the type of the comparator.
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return __comp;
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} else {
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return [&](auto&& __lhs, auto&& __rhs) {
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return std::invoke(__comp,
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std::invoke(__proj, std::forward<decltype(__lhs)>(__lhs)),
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std::invoke(__proj, std::forward<decltype(__rhs)>(__rhs)));
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};
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}
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}
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} // namespace ranges
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
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#endif // _LIBCPP___ALGORITHM_MAKE_PROJECTED_H
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