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The C and C++ Include Header Files

/usr/include/c++/13/bits/invoke.h


$ cat -n /usr/include/c++/13/bits/invoke.h

     1	// Implementation of INVOKE -*- C++ -*-
     2	
     3	// Copyright (C) 2016-2023 Free Software Foundation, Inc.
     4	//
     5	// This file is part of the GNU ISO C++ Library.  This library is free
     6	// software; you can redistribute it and/or modify it under the
     7	// terms of the GNU General Public License as published by the
     8	// Free Software Foundation; either version 3, or (at your option)
     9	// any later version.
    10	
    11	// This library is distributed in the hope that it will be useful,
    12	// but WITHOUT ANY WARRANTY; without even the implied warranty of
    13	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    14	// GNU General Public License for more details.
    15	
    16	// Under Section 7 of GPL version 3, you are granted additional
    17	// permissions described in the GCC Runtime Library Exception, version
    18	// 3.1, as published by the Free Software Foundation.
    19	
    20	// You should have received a copy of the GNU General Public License and
    21	// a copy of the GCC Runtime Library Exception along with this program;
    22	// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    23	// <http://www.gnu.org/licenses/>.
    24	
    25	/** @file include/bits/invoke.h
    26	 *  This is an internal header file, included by other library headers.
    27	 *  Do not attempt to use it directly. @headername{functional}
    28	 */
    29	
    30	#ifndef _GLIBCXX_INVOKE_H
    31	#define _GLIBCXX_INVOKE_H 1
    32	
    33	#pragma GCC system_header
    34	
    35	#if __cplusplus < 201103L
    36	# include <bits/c++0x_warning.h>
    37	#else
    38	
    39	#include <type_traits>
    40	#include <bits/move.h> // forward
    41	
    42	namespace std _GLIBCXX_VISIBILITY(default)
    43	{
    44	_GLIBCXX_BEGIN_NAMESPACE_VERSION
    45	
    46	  /**
    47	   *  @addtogroup utilities
    48	   *  @{
    49	   */
    50	
    51	  // Used by __invoke_impl instead of std::forward<_Tp> so that a
    52	  // reference_wrapper is converted to an lvalue-reference.
    53	  template<typename _Tp, typename _Up = typename __inv_unwrap<_Tp>::type>
    54	    constexpr _Up&&
    55	    __invfwd(typename remove_reference<_Tp>::type& __t) noexcept
    56	    { return static_cast<_Up&&>(__t); }
    57	
    58	  template<typename _Res, typename _Fn, typename... _Args>
    59	    constexpr _Res
    60	    __invoke_impl(__invoke_other, _Fn&& __f, _Args&&... __args)
    61	    { return std::forward<_Fn>(__f)(std::forward<_Args>(__args)...); }
    62	
    63	  template<typename _Res, typename _MemFun, typename _Tp, typename... _Args>
    64	    constexpr _Res
    65	    __invoke_impl(__invoke_memfun_ref, _MemFun&& __f, _Tp&& __t,
    66			  _Args&&... __args)
    67	    { return (__invfwd<_Tp>(__t).*__f)(std::forward<_Args>(__args)...); }
    68	
    69	  template<typename _Res, typename _MemFun, typename _Tp, typename... _Args>
    70	    constexpr _Res
    71	    __invoke_impl(__invoke_memfun_deref, _MemFun&& __f, _Tp&& __t,
    72			  _Args&&... __args)
    73	    {
    74	      return ((*std::forward<_Tp>(__t)).*__f)(std::forward<_Args>(__args)...);
    75	    }
    76	
    77	  template<typename _Res, typename _MemPtr, typename _Tp>
    78	    constexpr _Res
    79	    __invoke_impl(__invoke_memobj_ref, _MemPtr&& __f, _Tp&& __t)
    80	    { return __invfwd<_Tp>(__t).*__f; }
    81	
    82	  template<typename _Res, typename _MemPtr, typename _Tp>
    83	    constexpr _Res
    84	    __invoke_impl(__invoke_memobj_deref, _MemPtr&& __f, _Tp&& __t)
    85	    { return (*std::forward<_Tp>(__t)).*__f; }
    86	
    87	  /// Invoke a callable object.
    88	  template<typename _Callable, typename... _Args>
    89	    constexpr typename __invoke_result<_Callable, _Args...>::type
    90	    __invoke(_Callable&& __fn, _Args&&... __args)
    91	    noexcept(__is_nothrow_invocable<_Callable, _Args...>::value)
    92	    {
    93	      using __result = __invoke_result<_Callable, _Args...>;
    94	      using __type = typename __result::type;
    95	      using __tag = typename __result::__invoke_type;
    96	      return std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
    97						std::forward<_Args>(__args)...);
    98	    }
    99	
   100	#if __cplusplus >= 201703L
   101	  // INVOKE<R>: Invoke a callable object and convert the result to R.
   102	  template<typename _Res, typename _Callable, typename... _Args>
   103	    constexpr enable_if_t<is_invocable_r_v<_Res, _Callable, _Args...>, _Res>
   104	    __invoke_r(_Callable&& __fn, _Args&&... __args)
   105	    noexcept(is_nothrow_invocable_r_v<_Res, _Callable, _Args...>)
   106	    {
   107	      using __result = __invoke_result<_Callable, _Args...>;
   108	      using __type = typename __result::type;
   109	      using __tag = typename __result::__invoke_type;
   110	      if constexpr (is_void_v<_Res>)
   111		std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
   112						std::forward<_Args>(__args)...);
   113	      else
   114		return std::__invoke_impl<__type>(__tag{},
   115						  std::forward<_Callable>(__fn),
   116						  std::forward<_Args>(__args)...);
   117	    }
   118	#else // C++11 or C++14
   119	  // This is a non-SFINAE-friendly std::invoke_r<R>(fn, args...) for C++11/14.
   120	  // It's used in std::function, std::bind, and std::packaged_task. Only
   121	  // std::function is constrained on is_invocable_r, but that is checked on
   122	  // construction so doesn't need to be checked again when calling __invoke_r.
   123	  // Consequently, these __invoke_r overloads do not check for invocable
   124	  // arguments, nor check that the invoke result is convertible to R.
   125	
   126	  // INVOKE<R>: Invoke a callable object and convert the result to R.
   127	  template<typename _Res, typename _Callable, typename... _Args>
   128	    constexpr __enable_if_t<!is_void<_Res>::value, _Res>
   129	    __invoke_r(_Callable&& __fn, _Args&&... __args)
   130	    {
   131	      using __result = __invoke_result<_Callable, _Args...>;
   132	      using __type = typename __result::type;
   133	#if __has_builtin(__reference_converts_from_temporary)
   134	      static_assert(!__reference_converts_from_temporary(_Res, __type),
   135			    "INVOKE<R> must not create a dangling reference");
   136	#endif
   137	      using __tag = typename __result::__invoke_type;
   138	      return std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
   139						std::forward<_Args>(__args)...);
   140	    }
   141	
   142	  // INVOKE<R> when R is cv void
   143	  template<typename _Res, typename _Callable, typename... _Args>
   144	    _GLIBCXX14_CONSTEXPR __enable_if_t<is_void<_Res>::value, _Res>
   145	    __invoke_r(_Callable&& __fn, _Args&&... __args)
   146	    {
   147	      using __result = __invoke_result<_Callable, _Args...>;
   148	      using __type = typename __result::type;
   149	      using __tag = typename __result::__invoke_type;
   150	      std::__invoke_impl<__type>(__tag{}, std::forward<_Callable>(__fn),
   151					 std::forward<_Args>(__args)...);
   152	    }
   153	#endif // C++11 or C++14
   154	
   155	_GLIBCXX_END_NAMESPACE_VERSION
   156	} // namespace std
   157	
   158	#endif // C++11
   159	
   160	#endif // _GLIBCXX_INVOKE_H