ceph/src/boost/libs/type_erasure/example/convert.cpp

   1 // Boost.TypeErasure library
   2 //
   3 // Copyright 2012 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 #include <boost/type_erasure/any.hpp>
  12 #include <boost/type_erasure/builtin.hpp>
  13 #include <boost/type_erasure/operators.hpp>
  14 #include <ostream>
  15
  16 namespace mpl = boost::mpl;
  17 using namespace boost::type_erasure;
  18
  19 void convert1() {
  20 //[convert1
  21     /*`
  22         An __any can be converted to another __any
  23         as long as the conversion is an "upcast."
  24     */
  25
  26     typedef any<
  27         mpl::vector<
  28             copy_constructible<>,
  29             typeid_<>,
  30             ostreamable<>
  31         >
  32     > any_printable;
  33     typedef any<
  34         mpl::vector<
  35             copy_constructible<>,
  36             typeid_<>
  37         >
  38     > common_any;
  39     any_printable x(10);
  40     common_any y(x);
  41
  42     /*`
  43         This conversion is okay because the requirements of `common_any`
  44         are a subset of the requirements of `any_printable`.  Conversion
  45         in the other direction is illegal.
  46
  47         ``
  48             common_any x(10);
  49             any_printable y(x); // error
  50         ``
  51     */
  52 //]
  53 }
  54
  55 //[convert
  56 //` (For the source of the examples in this section see
  57 //` [@boost:/libs/type_erasure/example/convert.cpp convert.cpp])
  58 //` [convert1]
  59 //]