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, class = enable_if_t<
46     _And<
47         is_constructible<decay_t<_Fn>, _Fn>,
48         is_move_constructible<decay_t<_Fn>>,
49         is_constructible<decay_t<_Args>, _Args>...,
50         is_move_constructible<decay_t<_Args>>...
51     >::value
52 >>
53 _LIBCPP_HIDE_FROM_ABI
54 constexpr auto bind_front(_Fn&& __f, _Args&&... __args) {
55     return __bind_front_t<decay_t<_Fn>, decay_t<_Args>...>(_VSTD::forward<_Fn>(__f), _VSTD::forward<_Args>(__args)...);
56 }
57 
58 #endif // _LIBCPP_STD_VER >= 20
59 
60 _LIBCPP_END_NAMESPACE_STD
61 
62 #endif // _LIBCPP___FUNCTIONAL_BIND_FRONT_H
63