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