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>
  17 #include <utility>
  18
  19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  20 #pragma GCC system_header
  21 #endif
  22
  23 _LIBCPP_BEGIN_NAMESPACE_STD
  24
  25 #if _LIBCPP_STD_VER > 17
  26
  27 struct __bind_front_op {
  28     template <class ..._Args>
  29     _LIBCPP_HIDE_FROM_ABI
  30     constexpr auto operator()(_Args&& ...__args) const
  31         noexcept(noexcept(_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
  32         -> decltype(      _VSTD::invoke(_VSTD::forward<_Args>(__args)...))
  33         { return          _VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
  34 };
  35
  36 template <class _Fn, class ..._BoundArgs>
  37 struct __bind_front_t : __perfect_forward<__bind_front_op, _Fn, _BoundArgs...> {
  38     using __perfect_forward<__bind_front_op, _Fn, _BoundArgs...>::__perfect_forward;
  39 };
  40
  41 template <class _Fn, class... _Args, class = enable_if_t<
  42     _And<
  43         is_constructible<decay_t<_Fn>, _Fn>,
  44         is_move_constructible<decay_t<_Fn>>,
  45         is_constructible<decay_t<_Args>, _Args>...,
  46         is_move_constructible<decay_t<_Args>>...
  47     >::value
  48 >>
  49 _LIBCPP_HIDE_FROM_ABI
  50 constexpr auto bind_front(_Fn&& __f, _Args&&... __args) {
  51     return __bind_front_t<decay_t<_Fn>, decay_t<_Args>...>(_VSTD::forward<_Fn>(__f), _VSTD::forward<_Args>(__args)...);
  52 }
  53
  54 #endif // _LIBCPP_STD_VER > 17
  55
  56 _LIBCPP_END_NAMESPACE_STD
  57
  58 #endif // _LIBCPP___FUNCTIONAL_BIND_FRONT_H