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- //
- // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
- //
- // Distributed under the Boost Software License, Version 1.0. (See accompanying
- // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
- //
- // Official repository: https://github.com/boostorg/beast
- //
- #ifndef BOOST_BEAST_DETAIL_IS_INVOCABLE_HPP
- #define BOOST_BEAST_DETAIL_IS_INVOCABLE_HPP
- #include <type_traits>
- #include <utility>
- namespace boost {
- namespace beast {
- namespace detail {
- template<class R, class C, class ...A>
- auto
- is_invocable_test(C&& c, int, A&& ...a)
- -> decltype(std::is_convertible<
- decltype(c(std::forward<A>(a)...)), R>::value ||
- std::is_same<R, void>::value,
- std::true_type());
- template<class R, class C, class ...A>
- std::false_type
- is_invocable_test(C&& c, long, A&& ...a);
- /** Metafunction returns `true` if F callable as R(A...)
- Example:
- @code
- is_invocable<T, void(std::string)>::value
- @endcode
- */
- /** @{ */
- template<class C, class F>
- struct is_invocable : std::false_type
- {
- };
- template<class C, class R, class ...A>
- struct is_invocable<C, R(A...)>
- : decltype(is_invocable_test<R>(
- std::declval<C>(), 1, std::declval<A>()...))
- {
- };
- /** @} */
- } // detail
- } // beast
- } // boost
- #endif
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