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 #ifndef _LIBCPP___RANGES_EMPTY_VIEW_H 10 #define _LIBCPP___RANGES_EMPTY_VIEW_H 11 12 #include <__config> 13 #include <__ranges/enable_borrowed_range.h> 14 #include <__ranges/view_interface.h> 15 #include <type_traits> 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 !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 24 25 namespace ranges { 26 template<class _Tp> 27 requires is_object_v<_Tp> 28 class empty_view : public view_interface<empty_view<_Tp>> { 29 public: 30 _LIBCPP_HIDE_FROM_ABI static constexpr _Tp* begin() noexcept { return nullptr; } 31 _LIBCPP_HIDE_FROM_ABI static constexpr _Tp* end() noexcept { return nullptr; } 32 _LIBCPP_HIDE_FROM_ABI static constexpr _Tp* data() noexcept { return nullptr; } 33 _LIBCPP_HIDE_FROM_ABI static constexpr size_t size() noexcept { return 0; } 34 _LIBCPP_HIDE_FROM_ABI static constexpr bool empty() noexcept { return true; } 35 }; 36 37 template<class _Tp> 38 inline constexpr bool enable_borrowed_range<empty_view<_Tp>> = true; 39 } // namespace ranges 40 41 #endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 42 43 _LIBCPP_END_NAMESPACE_STD 44 45 #endif // _LIBCPP___RANGES_EMPTY_VIEW_H 46