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/conditional.h> 14 #include <__type_traits/enable_if.h> 15 #include <__type_traits/integral_constant.h> 16 #include <__type_traits/is_same.h> 17 18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 19 # pragma GCC system_header 20 #endif 21 22 _LIBCPP_BEGIN_NAMESPACE_STD 23 24 template <class...> 25 using __expand_to_true = true_type; 26 27 template <class... _Pred> 28 __expand_to_true<__enable_if_t<_Pred::value>...> __and_helper(int); 29 30 template <class...> 31 false_type __and_helper(...); 32 33 // _And always performs lazy evaluation of its arguments. 34 // 35 // However, `_And<_Pred...>` itself will evaluate its result immediately (without having to 36 // be instantiated) since it is an alias, unlike `conjunction<_Pred...>`, which is a struct. 37 // If you want to defer the evaluation of `_And<_Pred...>` itself, use `_Lazy<_And, _Pred...>`. 38 template <class... _Pred> 39 using _And _LIBCPP_NODEBUG = decltype(std::__and_helper<_Pred...>(0)); 40 41 template <bool... _Preds> 42 struct __all_dummy; 43 44 template <bool... _Pred> 45 struct __all : _IsSame<__all_dummy<_Pred...>, __all_dummy<((void)_Pred, true)...> > {}; 46 47 #if _LIBCPP_STD_VER >= 17 48 49 template <class...> 50 struct conjunction : true_type {}; 51 52 template <class _Arg> 53 struct conjunction<_Arg> : _Arg {}; 54 55 template <class _Arg, class... _Args> 56 struct conjunction<_Arg, _Args...> : conditional_t<!bool(_Arg::value), _Arg, conjunction<_Args...>> {}; 57 58 template <class... _Args> 59 inline constexpr bool conjunction_v = conjunction<_Args...>::value; 60 61 #endif // _LIBCPP_STD_VER >= 17 62 63 _LIBCPP_END_NAMESPACE_STD 64 65 #endif // _LIBCPP___TYPE_TRAITS_CONJUNCTION_H 66