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Diffstat (limited to 'boost/poly_collection/detail/is_invocable.hpp')
-rw-r--r-- | boost/poly_collection/detail/is_invocable.hpp | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/boost/poly_collection/detail/is_invocable.hpp b/boost/poly_collection/detail/is_invocable.hpp new file mode 100644 index 0000000000..c93ba476b7 --- /dev/null +++ b/boost/poly_collection/detail/is_invocable.hpp @@ -0,0 +1,97 @@ +/* Copyright 2016-2017 Joaquin M Lopez Munoz. + * 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) + * + * See http://www.boost.org/libs/poly_collection for library home page. + */ + +#ifndef BOOST_POLY_COLLECTION_DETAIL_IS_INVOCABLE_HPP +#define BOOST_POLY_COLLECTION_DETAIL_IS_INVOCABLE_HPP + +#if defined(_MSC_VER) +#pragma once +#endif + +#include <functional> +#include <type_traits> + +/* technique explained at + * http://bannalia.blogspot.com/2016/09/compile-time-checking-existence-of.html + */ + +namespace boost{ +namespace poly_collection{ +namespace detail{ +namespace is_invocable_fallback{ + +template <typename F,typename... Args> +struct is_invocable: + std::is_constructible< + std::function<void(Args...)>, + std::reference_wrapper<typename std::remove_reference<F>::type> + > +{}; + +template <typename R,typename F,typename... Args> +struct is_invocable_r: + std::is_constructible< + std::function<R(Args...)>, + std::reference_wrapper<typename std::remove_reference<F>::type> + > +{}; + +struct hook{}; + +}}}} + +namespace std{ + +template<> +struct is_void< ::boost::poly_collection::detail::is_invocable_fallback::hook>: + std::false_type +{ + template<typename F,typename... Args> + static constexpr bool is_invocable_f() + { + using namespace ::boost::poly_collection::detail::is_invocable_fallback; + return is_invocable<F,Args...>::value; + } + + template<typename R,typename F,typename... Args> + static constexpr bool is_invocable_r_f() + { + using namespace ::boost::poly_collection::detail::is_invocable_fallback; + return is_invocable_r<R,F,Args...>::value; + } +}; + +} /* namespace std */ + +namespace boost{ + +namespace poly_collection{ + +namespace detail{ + +template<typename F,typename... Args> +struct is_invocable:std::integral_constant< + bool, + std::is_void<is_invocable_fallback::hook>::template + is_invocable_f<F,Args...>() +>{}; + +template<typename R,typename F,typename... Args> +struct is_invocable_r:std::integral_constant< + bool, + std::is_void<is_invocable_fallback::hook>::template + is_invocable_r_f<R,F,Args...>() +>{}; + +} /* namespace poly_collection::detail */ + +} /* namespace poly_collection */ + +} /* namespace boost */ + +#endif |