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- /*!
- * \file sfinae.h
- * \brief Template meta-programming SFINAE helpers
- */
- #ifndef __utl_meta_sfinae_h__
- #define __utl_meta_sfinae_h__
-
- #include <utl/core/impl.h>
- #include <utl/meta/basic.h>
- #include <type_traits>
-
- /*!
- * \ingroup meta
- * \defgroup sfinae SFINAE
- * conditional use support header.
- */
- //! @{
- namespace utl {
- namespace meta {
-
- //! \name enable_if from STL
- //! @{
-
- //! enable_if, imported from stl
- template <bool If, typename _Tp = void> using enable_if = std::enable_if<If, _Tp>;
-
- //! alias template for enable_if
- template<bool If, typename _Tp = void> using enable_if_t = eval< enable_if<If, _Tp> >;
-
- //! @}
-
- //! \name when implementation
- //! @{
- namespace details {
- // template <typename... T>
- // struct dev_null { using type = dev_null; }; //< Same as typelist
-
- template <bool If> struct when_ { };
- template <> struct when_<true> { using type = void; };
- }
- //! Tool to enable a partial specialization only if a boolean condition is true.
- //! Well formed only if \p If is true
- template <bool If>
- using when = eval< details::when_<If> >;
-
- // //! Well formed only if all of \p Ifs are \c true
- // template <bool ...Ifs>
- // using when_all = details::dev_null<
- // when<Ifs>...
- // >;
-
- //! @}
-
- //! If same type resolves to _Ret, else SFINAE
- template <typename _T1, typename _T2, typename _Ret =_T1>
- using use_if_same_t = enable_if_t<
- same<_T1, _T2>::value, _Ret
- >;
- //! If not same type resolves to _Ret, else SFINAE
- template <typename _T1, typename _T2, typename _Ret =_T1>
- using use_if_not_same_t = enable_if_t<
- !same<_T1, _T2>::value, _Ret
- >;
- //! If any type (_T1 or _T2) type resolves to _Ret, else to SFINAE
- template <typename T1, typename... Ts>
- using use_if_any_t = enable_if_t<
- or_<T1, Ts...>::value, T1
- >;
-
- //! If both type (_T1 and _T2) type resolves to _Ret, else to SFINAE
- template <typename T1, typename... Ts>
- using use_if_all_t = enable_if_t<
- and_<T1, Ts...>::value, T1
- >;
-
-
-
- }}
-
- //! @}
-
- #endif /* __utl_meta_sfinae_h__ */
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