boost/type_erasure/rebind_any.hpp
// Boost.TypeErasure library
//
// Copyright 2011 Steven Watanabe
//
// Distributed under 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)
//
// $Id$
#ifndef BOOST_TYPE_ERASURE_REBIND_ANY_HPP_INCLUDED
#define BOOST_TYPE_ERASURE_REBIND_ANY_HPP_INCLUDED
#include <boost/mpl/if.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/type_erasure/is_placeholder.hpp>
#include <boost/type_erasure/concept_of.hpp>
namespace boost {
namespace type_erasure {
template<class Concept, class T>
class any;
/**
* A metafunction that changes the @ref placeholder of
* an @ref any. If @c T is not a placeholder,
* returns @c T unchanged. This class is intended
* to be used in @ref concept_interface to deduce
* the argument types from the arguments of the concept.
*
* @pre Any must be a specialization of @ref any or a base
* class of such a specialization.
*
* \code
* rebind_any<any<Concept>, _a>::type -> any<Concept, _a>
* rebind_any<any<Concept>, _b&>::type -> any<Concept, _b&>
* rebind_any<any<Concept>, int>::type -> int
* \endcode
*
* @see derived, as_param
*/
template<class Any, class T>
struct rebind_any
{
#ifdef BOOST_TYPE_ERASURE_DOXYGEN
typedef detail::unspecified type;
#else
typedef typename ::boost::mpl::if_<
::boost::type_erasure::is_placeholder<
typename ::boost::remove_cv<
typename ::boost::remove_reference<T>::type
>::type
>,
::boost::type_erasure::any<
typename ::boost::type_erasure::concept_of<Any>::type,
T
>,
T
>::type type;
#endif
};
}
}
#endif