llvm-project/libcxx/include/__functional/identity.h

47 lines
1.1 KiB
C++

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___FUNCTIONAL_IDENTITY_H
#define _LIBCPP___FUNCTIONAL_IDENTITY_H
#include <__config>
#include <__utility/forward.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
struct __identity {
template <class _Tp>
_LIBCPP_NODISCARD _LIBCPP_CONSTEXPR _Tp&& operator()(_Tp&& __t) const _NOEXCEPT {
return std::forward<_Tp>(__t);
}
using is_transparent = void;
};
#if _LIBCPP_STD_VER > 17
struct identity {
template<class _Tp>
_LIBCPP_NODISCARD_EXT constexpr _Tp&& operator()(_Tp&& __t) const noexcept
{
return _VSTD::forward<_Tp>(__t);
}
using is_transparent = void;
};
#endif // _LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___FUNCTIONAL_IDENTITY_H