ceph/src/boost/libs/type_erasure/include/boost/type_erasure/rebind_any.hpp

   1 // Boost.TypeErasure library
   2 //
   3 // Copyright 2011 Steven Watanabe
   4 //
   5 // Distributed under the Boost Software License Version 1.0. (See
   6 // accompanying file LICENSE_1_0.txt or copy at
   7 // http://www.boost.org/LICENSE_1_0.txt)
   8 //
   9 // $Id$
  10
  11 #ifndef BOOST_TYPE_ERASURE_REBIND_ANY_HPP_INCLUDED
  12 #define BOOST_TYPE_ERASURE_REBIND_ANY_HPP_INCLUDED
  13
  14 #include <boost/mpl/if.hpp>
  15 #include <boost/type_traits/remove_cv.hpp>
  16 #include <boost/type_traits/remove_reference.hpp>
  17 #include <boost/type_erasure/is_placeholder.hpp>
  18 #include <boost/type_erasure/concept_of.hpp>
  19
  20 namespace boost {
  21 namespace type_erasure {
  22
  23 template<class Concept, class T>
  24 class any;
  25
  26 /**
  27  * A metafunction that changes the @ref placeholder of
  28  * an @ref any.  If @c T is not a placeholder,
  29  * returns @c T unchanged.  This class is intended
  30  * to be used in @ref concept_interface to deduce
  31  * the argument types from the arguments of the concept.
  32  *
  33  * @pre Any must be a specialization of @ref any or a base
  34  *      class of such a specialization.
  35  *
  36  * \code
  37  * rebind_any<any<Concept>, _a>::type -> any<Concept, _a>
  38  * rebind_any<any<Concept>, _b&>::type -> any<Concept, _b&>
  39  * rebind_any<any<Concept>, int>::type -> int
  40  * \endcode
  41  *
  42  * @see derived, as_param
  43  */
  44 template<class Any, class T>
  45 struct rebind_any
  46 {
  47 #ifdef BOOST_TYPE_ERASURE_DOXYGEN
  48     typedef detail::unspecified type;
  49 #else
  50     typedef typename ::boost::mpl::if_<
  51         ::boost::type_erasure::is_placeholder<
  52             typename ::boost::remove_cv<
  53                 typename ::boost::remove_reference<T>::type
  54             >::type
  55         >,
  56         ::boost::type_erasure::any<
  57             typename ::boost::type_erasure::concept_of<Any>::type,
  58             T
  59         >,
  60         T
  61     >::type type;
  62 #endif
  63 };
  64
  65 }
  66 }
  67
  68 #endif