ceph/src/boost/boost/spirit/home/x3/support/traits/variant_has_substitute.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 Joel de Guzman
   3     http://spirit.sourceforge.net/
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 =============================================================================*/
   8 #if !defined(BOOST_SPIRIT_X3_VARIANT_HAS_SUBSTITUTE_APR_18_2014_925AM)
   9 #define BOOST_SPIRIT_X3_VARIANT_HAS_SUBSTITUTE_APR_18_2014_925AM
  10
  11 #include <boost/spirit/home/x3/support/traits/is_substitute.hpp>
  12 #include <boost/mpl/find.hpp>
  13
  14 namespace boost { namespace spirit { namespace x3 { namespace traits
  15 {
  16     template <typename Variant, typename Attribute>
  17     struct variant_has_substitute_impl
  18     {
  19         // Find a type from the variant that can be a substitute for Attribute.
  20         // return true_ if one is found, else false_
  21
  22         typedef Variant variant_type;
  23         typedef typename variant_type::types types;
  24         typedef typename mpl::end<types>::type end;
  25
  26         typedef typename mpl::find<types, Attribute>::type iter_1;
  27
  28         typedef typename
  29             mpl::eval_if<
  30                 is_same<iter_1, end>,
  31                 mpl::find_if<types, traits::is_substitute<mpl::_1, Attribute>>,
  32                 mpl::identity<iter_1>
  33             >::type
  34         iter;
  35
  36         typedef mpl::not_<is_same<iter, end>> type;
  37     };
  38
  39     template <typename Variant, typename Attribute>
  40     struct variant_has_substitute
  41         : variant_has_substitute_impl<Variant, Attribute>::type {};
  42
  43     template <typename Attribute>
  44     struct variant_has_substitute<unused_type, Attribute> : mpl::true_ {};
  45
  46     template <typename Attribute>
  47     struct variant_has_substitute<unused_type const, Attribute> : mpl::true_ {};
  48
  49 }}}}
  50
  51 #endif