/*=============================================================================
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