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freebsd
GitHub Repository: freebsd/freebsd-src
 Path: blob/main/contrib/llvm-project/libcxx/include/__functional/perfect_forward.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___FUNCTIONAL_PERFECT_FORWARD_H

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#define _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H

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#include <__config>

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#include <__type_traits/enable_if.h>

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#include <__type_traits/invoke.h>

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#include <__type_traits/is_constructible.h>

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#include <__utility/declval.h>

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#include <__utility/forward.h>

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#include <__utility/integer_sequence.h>

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#include <__utility/move.h>

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#include <tuple>

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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_PUSH_MACROS

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#include <__undef_macros>

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_LIBCPP_BEGIN_NAMESPACE_STD

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#if _LIBCPP_STD_VER >= 17

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template <class _Op, class _Indices, class... _BoundArgs>

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struct __perfect_forward_impl;

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template <class _Op, size_t... _Idx, class... _BoundArgs>

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struct __perfect_forward_impl<_Op, index_sequence<_Idx...>, _BoundArgs...> {

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private:

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  tuple<_BoundArgs...> __bound_args_;

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public:

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  template <class... _Args, class = enable_if_t< is_constructible_v<tuple<_BoundArgs...>, _Args&&...> >>

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  _LIBCPP_HIDE_FROM_ABI explicit constexpr __perfect_forward_impl(_Args&&... __bound_args)

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      : __bound_args_(std::forward<_Args>(__bound_args)...) {}

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  _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl const&) = default;

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  _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl&&)      = default;

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  _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl const&) = default;

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  _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl&&)      = default;

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  template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs&..., _Args...>>>

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  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) & noexcept(

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      noexcept(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)))

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      -> decltype(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)) {

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    return _Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...);

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  }

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  template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs&..., _Args...>>>

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  auto operator()(_Args&&...) & = delete;

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  template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const&..., _Args...>>>

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  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const& noexcept(

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      noexcept(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)))

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      -> decltype(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)) {

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    return _Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...);

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  }

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  template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const&..., _Args...>>>

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  auto operator()(_Args&&...) const& = delete;

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  template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs..., _Args...>>>

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  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) && noexcept(

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      noexcept(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)))

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      -> decltype(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)) {

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    return _Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...);

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  }

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  template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs..., _Args...>>>

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  auto operator()(_Args&&...) && = delete;

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  template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const..., _Args...>>>

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  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const&& noexcept(

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      noexcept(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)))

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      -> decltype(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)) {

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    return _Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...);

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  }

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  template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const..., _Args...>>>

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  auto operator()(_Args&&...) const&& = delete;

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};

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// __perfect_forward implements a perfect-forwarding call wrapper as explained in [func.require].

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template <class _Op, class... _Args>

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using __perfect_forward = __perfect_forward_impl<_Op, index_sequence_for<_Args...>, _Args...>;

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#endif // _LIBCPP_STD_VER >= 17

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_LIBCPP_END_NAMESPACE_STD

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_LIBCPP_POP_MACROS

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#endif // _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H

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