boost_iterator/include/boost/pointee.hpp

#ifndef POINTEE_DWA200415_HPP
# define POINTEE_DWA200415_HPP

//
// Copyright David Abrahams 2004. 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)
//
// typename pointee<P>::type provides the pointee type of P.
//
// For example, it is T for T* and X for shared_ptr<X>.
//
// http://www.boost.org/libs/iterator/doc/pointee.html
//

# include <boost/detail/is_incrementable.hpp>
# include <boost/iterator/iterator_traits.hpp>
# include <boost/mpl/eval_if.hpp>

#include <iterator>
#include <type_traits>

namespace boost {

namespace detail
{
  template <class P>
  struct smart_ptr_pointee
  {
      typedef typename P::element_type type;
  };

  template <class Iterator>
  struct iterator_pointee
  {
      typedef typename std::iterator_traits<Iterator>::value_type value_type;

      typedef typename std::conditional<
          std::is_const<
              typename std::remove_reference<decltype(*std::declval<Iterator&>())>::type
          >::value
        , typename std::add_const<value_type>::type
        , value_type
      >::type type;
  };
}

template <class P>
struct pointee
  : mpl::eval_if<
        detail::is_incrementable<P>
      , detail::iterator_pointee<P>
      , detail::smart_ptr_pointee<P>
    >
{
};

} // namespace boost

#endif // POINTEE_DWA200415_HPP