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 #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 _LIBCPP_STD_VER > 17 24 25 namespace ranges { 26 27 struct view_base { }; 28 29 template<class _Derived> 30 requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>> 31 class view_interface; 32 33 template<class _Op, class _Yp> 34 requires is_convertible_v<_Op*, view_interface<_Yp>*> 35 void __is_derived_from_view_interface(const _Op*, const view_interface<_Yp>*); 36 37 template <class _Tp> 38 inline constexpr bool enable_view = derived_from<_Tp, view_base> || 39 requires { ranges::__is_derived_from_view_interface((_Tp*)nullptr, (_Tp*)nullptr); }; 40 41 } // namespace ranges 42 43 #endif // _LIBCPP_STD_VER > 17 44 45 _LIBCPP_END_NAMESPACE_STD 46 47 #endif // _LIBCPP___RANGES_ENABLE_VIEW_H 48