| //===----------------------------------------------------------------------===// |
| // |
| // 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_CONDITIONAL_H |
| #define _LIBCPP___TYPE_TRAITS_CONDITIONAL_H |
| |
| #include <__config> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| # pragma GCC system_header |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| template <bool> |
| struct _IfImpl; |
| |
| template <> |
| struct _IfImpl<true> { |
| template <class _IfRes, class _ElseRes> |
| using _Select _LIBCPP_NODEBUG = _IfRes; |
| }; |
| |
| template <> |
| struct _IfImpl<false> { |
| template <class _IfRes, class _ElseRes> |
| using _Select _LIBCPP_NODEBUG = _ElseRes; |
| }; |
| |
| template <bool _Cond, class _IfRes, class _ElseRes> |
| using _If _LIBCPP_NODEBUG = typename _IfImpl<_Cond>::template _Select<_IfRes, _ElseRes>; |
| |
| template <bool _Bp, class _If, class _Then> |
| struct _LIBCPP_TEMPLATE_VIS conditional { |
| using type _LIBCPP_NODEBUG = _If; |
| }; |
| template <class _If, class _Then> |
| struct _LIBCPP_TEMPLATE_VIS conditional<false, _If, _Then> { |
| using type _LIBCPP_NODEBUG = _Then; |
| }; |
| |
| #if _LIBCPP_STD_VER >= 14 |
| template <bool _Bp, class _IfRes, class _ElseRes> |
| using conditional_t _LIBCPP_NODEBUG = typename conditional<_Bp, _IfRes, _ElseRes>::type; |
| #endif |
| |
| // Helper so we can use "conditional_t" in all language versions. |
| template <bool _Bp, class _If, class _Then> |
| using __conditional_t _LIBCPP_NODEBUG = typename conditional<_Bp, _If, _Then>::type; |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___TYPE_TRAITS_CONDITIONAL_H |