| //===----------------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef _LIBCPP___TYPE_TRAITS_DISJUNCTION_H |
| #define _LIBCPP___TYPE_TRAITS_DISJUNCTION_H |
| |
| #include <__config> |
| #include <__type_traits/integral_constant.h> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| # pragma GCC system_header |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| template <bool> |
| struct _OrImpl; |
| |
| template <> |
| struct _OrImpl<true> { |
| template <class _Res, class _First, class... _Rest> |
| using _Result _LIBCPP_NODEBUG = |
| typename _OrImpl<!bool(_First::value) && sizeof...(_Rest) != 0>::template _Result<_First, _Rest...>; |
| }; |
| |
| template <> |
| struct _OrImpl<false> { |
| template <class _Res, class...> |
| using _Result = _Res; |
| }; |
| |
| // _Or always performs lazy evaluation of its arguments. |
| // |
| // However, `_Or<_Pred...>` itself will evaluate its result immediately (without having to |
| // be instantiated) since it is an alias, unlike `disjunction<_Pred...>`, which is a struct. |
| // If you want to defer the evaluation of `_Or<_Pred...>` itself, use `_Lazy<_Or, _Pred...>` |
| // or `disjunction<_Pred...>` directly. |
| template <class... _Args> |
| using _Or _LIBCPP_NODEBUG = typename _OrImpl<sizeof...(_Args) != 0>::template _Result<false_type, _Args...>; |
| |
| #if _LIBCPP_STD_VER >= 17 |
| |
| template <class... _Args> |
| struct disjunction : _Or<_Args...> {}; |
| |
| template <class... _Args> |
| inline constexpr bool disjunction_v = _Or<_Args...>::value; |
| |
| #endif // _LIBCPP_STD_VER >= 17 |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___TYPE_TRAITS_DISJUNCTION_H |