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___RANGES_ENABLE_VIEW_H 11 #define _LIBCPP___RANGES_ENABLE_VIEW_H 12 13 #include <__config> 14 #include <concepts> 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 !defined(_LIBCPP_HAS_NO_RANGES) 23 24 namespace ranges { 25 26 struct view_base { }; 27 28 template <class _Tp> 29 inline constexpr bool enable_view = derived_from<_Tp, view_base>; 30 31 } // end namespace ranges 32 33 #endif // !_LIBCPP_HAS_NO_RANGES 34 35 _LIBCPP_END_NAMESPACE_STD 36 37 #endif // _LIBCPP___RANGES_ENABLE_VIEW_H 38