v1/__iterator/empty.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___ITERATOR_EMPTY_H
0011 #define _LIBCPP___ITERATOR_EMPTY_H
0012
0013 #include <__config>
0014 #include <initializer_list>
0015
0016 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0017 #  pragma GCC system_header
0018 #endif
0019
0020 _LIBCPP_BEGIN_NAMESPACE_STD
0021
0022 #if _LIBCPP_STD_VER >= 17
0023
0024 template <class _Cont>
0025 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto
0026 empty(const _Cont& __c) noexcept(noexcept(__c.empty())) -> decltype(__c.empty()) {
0027   return __c.empty();
0028 }
0029
0030 template <class _Tp, size_t _Sz>
0031 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty(const _Tp (&)[_Sz]) noexcept {
0032   return false;
0033 }
0034
0035 template <class _Ep>
0036 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty(initializer_list<_Ep> __il) noexcept {
0037   return __il.size() == 0;
0038 }
0039
0040 #endif // _LIBCPP_STD_VER >= 17
0041
0042 _LIBCPP_END_NAMESPACE_STD
0043
0044 #endif // _LIBCPP___ITERATOR_EMPTY_H