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_PUSH_MACROS 21 #include <__undef_macros> 22 23 _LIBCPP_BEGIN_NAMESPACE_STD 24 25 #if !defined(_LIBCPP_HAS_NO_RANGES) 26 27 namespace ranges { 28 29 struct view_base { }; 30 31 template <class _Tp> 32 inline constexpr bool enable_view = derived_from<_Tp, view_base>; 33 34 } // end namespace ranges 35 36 #endif // !_LIBCPP_HAS_NO_RANGES 37 38 _LIBCPP_END_NAMESPACE_STD 39 40 _LIBCPP_POP_MACROS 41 42 #endif // _LIBCPP___RANGES_ENABLE_VIEW_H 43