// Boost.Range library | |
// | |
// Copyright Arno Schoedl & Neil Groves 2009. | |
// 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_EXTRACT_OPTIONAL_TYPE_HPP_INCLUDED | |
#define BOOST_RANGE_DETAIL_EXTRACT_OPTIONAL_TYPE_HPP_INCLUDED | |
#if defined(_MSC_VER) && (_MSC_VER >= 1200) | |
# pragma once | |
#endif | |
#include <boost/config.hpp> | |
#ifdef BOOST_NO_PARTIAL_TEMPLATE_SPECIALIZATION | |
#define BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( a_typedef ) \ | |
template< typename C > \ | |
struct extract_ ## a_typedef \ | |
{ \ | |
typedef BOOST_DEDUCED_TYPENAME C::a_typedef type; \ | |
}; | |
#else | |
namespace boost { | |
namespace range_detail { | |
template< typename T > struct exists { typedef void type; }; | |
} | |
} | |
// Defines extract_some_typedef<T> which exposes T::some_typedef as | |
// extract_some_typedef<T>::type if T::some_typedef exists. Otherwise | |
// extract_some_typedef<T> is empty. | |
#define BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( a_typedef ) \ | |
template< typename C, typename Enable=void > \ | |
struct extract_ ## a_typedef \ | |
{}; \ | |
template< typename C > \ | |
struct extract_ ## a_typedef< C \ | |
, BOOST_DEDUCED_TYPENAME boost::range_detail::exists< BOOST_DEDUCED_TYPENAME C::a_typedef >::type \ | |
> { \ | |
typedef BOOST_DEDUCED_TYPENAME C::a_typedef type; \ | |
}; | |
#endif | |
#endif // include guard |