122 lines
2.9 KiB
C++
122 lines
2.9 KiB
C++
/*=============================================================================
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Copyright (c) 2015 Paul Fultz II
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can_be_called.h
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#ifndef BOOST_HOF_GUARD_CAN_BE_CALLED_H
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#define BOOST_HOF_GUARD_CAN_BE_CALLED_H
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#include <boost/hof/config.hpp>
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#include <boost/hof/detail/and.hpp>
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#include <boost/hof/detail/holder.hpp>
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#include <boost/hof/detail/using.hpp>
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namespace boost { namespace hof { namespace detail {
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#if BOOST_HOF_NO_EXPRESSION_SFINAE
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struct dont_care
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{
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dont_care(...);
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};
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template<class T>
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struct never_care
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{
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typedef dont_care type;
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};
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struct cant_be_called_type
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{};
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struct no_type
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{};
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template<class F>
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struct is_callable_wrapper_fallback
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{
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template<class... Ts>
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auto operator()(Ts&&...) const
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-> decltype(std::declval<F>()(std::declval<Ts>()...));
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};
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template<class T, class U=typename std::remove_cv<typename std::remove_reference<T>::type>::type>
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struct is_callable_wrapper_base
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: std::conditional<BOOST_HOF_IS_CLASS(U) && !BOOST_HOF_IS_FINAL(U), U, is_callable_wrapper_fallback<U>>
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{};
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template<class F, class... Ts>
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struct is_callable_wrapper : is_callable_wrapper_base<F>::type
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{
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is_callable_wrapper();
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typedef cant_be_called_type const &(*pointer_to_function)(typename never_care<Ts>::type...);
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operator pointer_to_function() const;
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};
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template<class T>
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struct not_
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: std::integral_constant<bool, !T::value>
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{};
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template<class F, class... Ts>
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struct can_be_called
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: not_<std::is_same<cant_be_called_type, typename std::decay<decltype(
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is_callable_wrapper<F, Ts...>()(std::declval<Ts>()...)
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)>::type>>
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{};
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template<class F, class... Ts>
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struct check_args;
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template<class Res, class... Ts, class... Us>
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struct check_args<Res(Us...), Ts...>
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: and_<std::is_convertible<Ts, Us>...>
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{};
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template<class Res, class... Ts, class... Us>
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struct can_be_called<Res(*)(Us...), Ts...>
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: std::conditional<sizeof...(Ts) == sizeof...(Us),
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check_args<Res(Us...), Ts...>,
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std::false_type
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>::type
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{};
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template<class Res, class... Ts, class... Us>
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struct can_be_called<Res(Us...), Ts...>
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: std::conditional<sizeof...(Ts) == sizeof...(Us),
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check_args<Res(Us...), Ts...>,
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std::false_type
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>::type
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{};
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#else
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template<class T>
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T&& called_val() noexcept;
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template<class... Ts>
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struct callable_args
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{};
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template<class F, class Args, class=void>
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struct can_be_called_impl
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: std::false_type
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{};
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template<class F, class... Args>
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struct can_be_called_impl<F, callable_args<Args...>, typename detail::holder<
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decltype( boost::hof::detail::called_val<F>()(boost::hof::detail::called_val<Args>()...) )
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>::type>
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: std::true_type
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{};
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template<class F, class... Ts>
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BOOST_HOF_USING(can_be_called, can_be_called_impl<F, detail::callable_args<Ts...>>);
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#endif
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}}} // namespace boost::hof
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#endif
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