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- /*=============================================================================
- Copyright (c) 2016 Paul Fultz II
- result_type.hpp
- 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)
- ==============================================================================*/
- #ifndef BOOST_HOF_GUARD_RESULT_TYPE_HPP
- #define BOOST_HOF_GUARD_RESULT_TYPE_HPP
- #include <boost/hof/detail/holder.hpp>
- #include <utility>
- namespace boost { namespace hof { namespace detail {
- template<class F, class=void>
- struct function_result_type
- {};
- template<class F>
- struct function_result_type<F, typename holder<
- typename F::result_type
- >::type>
- {
- typedef typename F::result_type result_type;
- };
- template<class F, class G, class=void>
- struct compose_function_result_type
- : function_result_type<F>
- {};
- template<class F, class G>
- struct compose_function_result_type<F, G, typename holder<
- decltype(std::declval<F>()(std::declval<typename G::result_type>()))
- >::type>
- {
- typedef decltype(std::declval<F>()(std::declval<typename G::result_type>())) result_type;
- };
- }}} // namespace boost::hof
- #endif
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