libcxx/include/__functional/bind_front.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___FUNCTIONAL_BIND_FRONT_H
  11 #define _LIBCPP___FUNCTIONAL_BIND_FRONT_H
  12
  13 #include <__config>
  14 #include <__functional/invoke.h>
  15 #include <__functional/perfect_forward.h>
  16 #include <__type_traits/conjunction.h>
  17 #include <__type_traits/decay.h>
  18 #include <__type_traits/enable_if.h>
  19 #include <__type_traits/is_constructible.h>
  20 #include <__type_traits/is_move_constructible.h>
  21 #include <__utility/forward.h>
  22
  23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  24 #  pragma GCC system_header
  25 #endif
  26
  27 _LIBCPP_BEGIN_NAMESPACE_STD
  28
  29 #if _LIBCPP_STD_VER >= 20
  30
  31 struct __bind_front_op {
  32     template <class ..._Args>
  33     _LIBCPP_HIDE_FROM_ABI
  34     constexpr auto operator()(_Args&& ...__args) const
  35         noexcept(noexcept(_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
  36         -> decltype(      _VSTD::invoke(_VSTD::forward<_Args>(__args)...))
  37         { return          _VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
  38 };
  39
  40 template <class _Fn, class ..._BoundArgs>
  41 struct __bind_front_t : __perfect_forward<__bind_front_op, _Fn, _BoundArgs...> {
  42     using __perfect_forward<__bind_front_op, _Fn, _BoundArgs...>::__perfect_forward;
  43 };
  44
  45 template <class _Fn, class... _Args>
  46   requires is_constructible_v<decay_t<_Fn>, _Fn> && is_move_constructible_v<decay_t<_Fn>> &&
  47            (is_constructible_v<decay_t<_Args>, _Args> && ...) && (is_move_constructible_v<decay_t<_Args>> && ...)
  48 _LIBCPP_HIDE_FROM_ABI
  49 constexpr auto bind_front(_Fn&& __f, _Args&&... __args) {
  50     return __bind_front_t<decay_t<_Fn>, decay_t<_Args>...>(_VSTD::forward<_Fn>(__f), _VSTD::forward<_Args>(__args)...);
  51 }
  52
  53 #endif // _LIBCPP_STD_VER >= 20
  54
  55 _LIBCPP_END_NAMESPACE_STD
  56
  57 #endif // _LIBCPP___FUNCTIONAL_BIND_FRONT_H