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 <cstddef>
  15 #include <initializer_list>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #  pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 #if _LIBCPP_STD_VER >= 17
  24
  25 template <class _Cont>
  26 _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
  27 constexpr auto empty(const _Cont& __c)
  28 _NOEXCEPT_(noexcept(__c.empty()))
  29 -> decltype        (__c.empty())
  30 { return            __c.empty(); }
  31
  32 template <class _Tp, size_t _Sz>
  33 _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
  34 constexpr bool empty(const _Tp (&)[_Sz]) noexcept { return false; }
  35
  36 template <class _Ep>
  37 _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
  38 constexpr bool empty(initializer_list<_Ep> __il) noexcept { return __il.size() == 0; }
  39
  40 #endif // _LIBCPP_STD_VER >= 17
  41
  42 _LIBCPP_END_NAMESPACE_STD
  43
  44 #endif // _LIBCPP___ITERATOR_EMPTY_H