Boost_1_39_0/boost/iterator/interoperable.hpp

   1 // (C) Copyright David Abrahams 2002.
   2 // (C) Copyright Jeremy Siek    2002.
   3 // (C) Copyright Thomas Witt    2002.
   4 // Distributed under the Boost Software License, Version 1.0. (See
   5 // accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt)
   7 #ifndef BOOST_INTEROPERABLE_23022003THW_HPP
   8 # define BOOST_INTEROPERABLE_23022003THW_HPP
   9
  10 # include <boost/mpl/bool.hpp>
  11 # include <boost/mpl/or.hpp>
  12
  13 # include <boost/type_traits/is_convertible.hpp>
  14
  15 # include <boost/iterator/detail/config_def.hpp> // must appear last
  16
  17 namespace boost
  18 {
  19
  20   //
  21   // Meta function that determines whether two
  22   // iterator types are considered interoperable.
  23   //
  24   // Two iterator types A,B are considered interoperable if either
  25   // A is convertible to B or vice versa.
  26   // This interoperability definition is in sync with the
  27   // standards requirements on constant/mutable container
  28   // iterators (23.1 [lib.container.requirements]).
  29   //
  30   // For compilers that don't support is_convertible
  31   // is_interoperable gives false positives. See comments
  32   // on operator implementation for consequences.
  33   //
  34   template <typename A, typename B>
  35   struct is_interoperable
  36 # ifdef BOOST_NO_STRICT_ITERATOR_INTEROPERABILITY
  37     : mpl::true_
  38 # else
  39     : mpl::or_<
  40           is_convertible< A, B >
  41         , is_convertible< B, A > >
  42 # endif
  43   {
  44   };
  45
  46 } // namespace boost
  47
  48 # include <boost/iterator/detail/config_undef.hpp>
  49
  50 #endif // BOOST_INTEROPERABLE_23022003THW_HPP