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 <__concepts/derived_from.h> 14 #include <__concepts/same_as.h> 15 #include <__config> 16 #include <__type_traits/is_class.h> 17 #include <__type_traits/is_convertible.h> 18 #include <__type_traits/remove_cv.h> 19 20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 21 # pragma GCC system_header 22 #endif 23 24 _LIBCPP_BEGIN_NAMESPACE_STD 25 26 #if _LIBCPP_STD_VER >= 20 27 28 namespace ranges { 29 30 struct view_base { }; 31 32 template<class _Derived> 33 requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>> 34 class view_interface; 35 36 template<class _Op, class _Yp> 37 requires is_convertible_v<_Op*, view_interface<_Yp>*> 38 void __is_derived_from_view_interface(const _Op*, const view_interface<_Yp>*); 39 40 template <class _Tp> 41 inline constexpr bool enable_view = derived_from<_Tp, view_base> || 42 requires { ranges::__is_derived_from_view_interface((_Tp*)nullptr, (_Tp*)nullptr); }; 43 44 } // namespace ranges 45 46 #endif // _LIBCPP_STD_VER >= 20 47 48 _LIBCPP_END_NAMESPACE_STD 49 50 #endif // _LIBCPP___RANGES_ENABLE_VIEW_H 51