libcxx/include/__iterator/empty.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___ITERATOR_EMPTY_H
  11 #define _LIBCPP___ITERATOR_EMPTY_H
  12
  13 #include <__config>
  14 #include <initializer_list>
  15
  16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  17 #  pragma GCC system_header
  18 #endif
  19
  20 _LIBCPP_BEGIN_NAMESPACE_STD
  21
  22 #if _LIBCPP_STD_VER >= 17
  23
  24 template <class _Cont>
  25 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto
  26 empty(const _Cont& __c) noexcept(noexcept(__c.empty())) -> decltype(__c.empty()) {
  27   return __c.empty();
  28 }
  29
  30 template <class _Tp, size_t _Sz>
  31 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty(const _Tp (&)[_Sz]) noexcept {
  32   return false;
  33 }
  34
  35 template <class _Ep>
  36 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty(initializer_list<_Ep> __il) noexcept {
  37   return __il.size() == 0;
  38 }
  39
  40 #endif // _LIBCPP_STD_VER >= 17
  41
  42 _LIBCPP_END_NAMESPACE_STD
  43
  44 #endif // _LIBCPP___ITERATOR_EMPTY_H