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 <iterator>
#include <type_traits>

namespace boost {
namespace detail {

template< typename P >
struct smart_ptr_pointee
{
    using type = typename P::element_type;
};

template< typename Iterator, typename = typename std::remove_reference<decltype(*std::declval<Iterator&>())>::type >
struct iterator_pointee
{
    using type = typename std::iterator_traits<Iterator>::value_type;
};

template< typename Iterator, typename Reference >
struct iterator_pointee< Iterator, const Reference >
{
    using type = typename std::add_const<typename std::iterator_traits<Iterator>::value_type>::type;
};

} // namespace detail

template< typename P >
struct pointee :
    public std::conditional<
        detail::is_incrementable<P>::value,
        detail::iterator_pointee<P>,
        detail::smart_ptr_pointee<P>
    >::type
{
};

} // namespace boost

#endif // POINTEE_DWA200415_HPP