Chris@102: // Boost.Range library
Chris@102: //
Chris@102: //  Copyright Neil Groves 2014. Use, modification and
Chris@102: //  distribution is subject to the Boost Software License, Version
Chris@102: //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@102: //  http://www.boost.org/LICENSE_1_0.txt)
Chris@102: //
Chris@102: // For more information, see http://www.boost.org/libs/range/
Chris@102: //
Chris@102: #ifndef BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED
Chris@102: #define BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED
Chris@102: 
Chris@102: #include <boost/optional/optional.hpp>
Chris@102: #include <boost/mpl/if.hpp>
Chris@102: #include <boost/type_traits/has_trivial_constructor.hpp>
Chris@102: 
Chris@102: namespace boost
Chris@102: {
Chris@102:     namespace range_detail
Chris@102:     {
Chris@102: 
Chris@102: template<typename F, typename R>
Chris@102: class default_constructible_unary_fn_wrapper
Chris@102: {
Chris@102: public:
Chris@102:     typedef R result_type;
Chris@102: 
Chris@102:     default_constructible_unary_fn_wrapper()
Chris@102:     {
Chris@102:     }
Chris@102:     default_constructible_unary_fn_wrapper(const F& source)
Chris@102:         : m_impl(source)
Chris@102:     {
Chris@102:     }
Chris@102:     template<typename Arg>
Chris@102:     R operator()(const Arg& arg) const
Chris@102:     {
Chris@102:         BOOST_ASSERT(m_impl);
Chris@102:         return (*m_impl)(arg);
Chris@102:     }
Chris@102:     template<typename Arg>
Chris@102:     R operator()(Arg& arg) const
Chris@102:     {
Chris@102:         BOOST_ASSERT(m_impl);
Chris@102:         return (*m_impl)(arg);
Chris@102:     }
Chris@102: private:
Chris@102:     boost::optional<F> m_impl;
Chris@102: };
Chris@102: 
Chris@102: template<typename F, typename R>
Chris@102: struct default_constructible_unary_fn_gen
Chris@102: {
Chris@102:     typedef typename boost::mpl::if_<
Chris@102:         boost::has_trivial_default_constructor<F>,
Chris@102:         F,
Chris@102:         default_constructible_unary_fn_wrapper<F,R>
Chris@102:     >::type type;
Chris@102: };
Chris@102: 
Chris@102:     } // namespace range_detail
Chris@102: } // namespace boost
Chris@102: 
Chris@102: #endif // include guard