arabica/include/Utils/getparam.hpp

#ifndef ARABICA_UTILS_GET_PARAM_HPP
#define ARABICA_UTILS_GET_PARAM_HPP

#ifdef HAVE_BOOST
#include <boost/mpl/if.hpp>
#include <boost/type_traits/is_base_and_derived.hpp>
#endif

namespace Arabica
{

struct nil_t { };

#ifdef HAVE_BOOST
template <typename BaseT, typename DefaultT, typename T0, typename T1>
struct get_param
{
  typedef typename boost::mpl::if_<
      boost::is_base_and_derived<BaseT, T0>
      , T0
      , typename boost::mpl::if_<
            boost::is_base_and_derived<BaseT, T1>
          , T1
          , DefaultT
        >::type
    >::type type;
}; // get_param
#else
template <typename BaseT, typename DefaultT, typename T0, typename T1>
struct get_param
{
  typedef T0 type;
};
#endif

} // namespace Arabica

#endif