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