1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___TYPE_TRAITS_CONJUNCTION_H 10 #define _LIBCPP___TYPE_TRAITS_CONJUNCTION_H 11 12 #include <__config> 13 #include <__type_traits/integral_constant.h> 14 #include <__type_traits/is_same.h> 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 template <bool> 23 struct _AndImpl; 24 25 template <> 26 struct _AndImpl<true> { 27 template <class _Res, class _First, class... _Rest> 28 using _Result _LIBCPP_NODEBUG = 29 typename _AndImpl<bool(_First::value) && sizeof...(_Rest) != 0>::template _Result<_First, _Rest...>; 30 }; 31 32 template <> 33 struct _AndImpl<false> { 34 template <class _Res, class...> 35 using _Result _LIBCPP_NODEBUG = _Res; 36 }; 37 38 // _And always performs lazy evaluation of its arguments. 39 // 40 // However, `_And<_Pred...>` itself will evaluate its result immediately (without having to 41 // be instantiated) since it is an alias, unlike `conjunction<_Pred...>`, which is a struct. 42 // If you want to defer the evaluation of `_And<_Pred...>` itself, use `_Lazy<_And, _Pred...>`. 43 template <class... _Args> 44 using _And _LIBCPP_NODEBUG = typename _AndImpl<sizeof...(_Args) != 0>::template _Result<true_type, _Args...>; 45 46 template <bool... _Preds> 47 struct __all_dummy; 48 49 template <bool... _Pred> 50 struct __all : _IsSame<__all_dummy<_Pred...>, __all_dummy<((void)_Pred, true)...> > {}; 51 52 #if _LIBCPP_STD_VER >= 17 53 54 template <class... _Args> 55 struct _LIBCPP_NO_SPECIALIZATIONS conjunction : _And<_Args...> {}; 56 57 template <class... _Args> 58 _LIBCPP_NO_SPECIALIZATIONS inline constexpr bool conjunction_v = _And<_Args...>::value; 59 60 #endif // _LIBCPP_STD_VER >= 17 61 62 _LIBCPP_END_NAMESPACE_STD 63 64 #endif // _LIBCPP___TYPE_TRAITS_CONJUNCTION_H 65