ceph/src/boost/boost/metaparse/v1/accept_when.hpp

   1 #ifndef BOOST_METAPARSE_V1_ACCEPT_WHEN_HPP
   2 #define BOOST_METAPARSE_V1_ACCEPT_WHEN_HPP
   3
   4 // Copyright Abel Sinkovics (abel@sinkovics.hu)  2009 - 2010.
   5 // Distributed under the Boost Software License, Version 1.0.
   6 //    (See accompanying file LICENSE_1_0.txt or copy at
   7 //          http://www.boost.org/LICENSE_1_0.txt)
   8
   9 #include <boost/metaparse/v1/get_result.hpp>
  10 #include <boost/metaparse/v1/reject.hpp>
  11 #include <boost/metaparse/v1/is_error.hpp>
  12
  13 #include <boost/mpl/if.hpp>
  14 #include <boost/mpl/eval_if.hpp>
  15
  16 namespace boost
  17 {
  18   namespace metaparse
  19   {
  20     namespace v1
  21     {
  22       template <class P, class Pred, class Msg>
  23       struct accept_when
  24       {
  25       private:
  26         struct unchecked
  27         {
  28           template <class S, class Pos>
  29           struct apply :
  30             boost::mpl::eval_if<
  31               typename Pred::template apply<
  32                 typename get_result<typename P::template apply<S, Pos> >::type
  33               >::type,
  34               typename P::template apply<S, Pos>,
  35               reject<Msg, Pos>
  36             >
  37           {};
  38         };
  39       public:
  40         typedef accept_when type;
  41
  42         template <class S, class Pos>
  43         struct apply :
  44           boost::mpl::if_<
  45             is_error<typename P::template apply<S, Pos> >,
  46             P,
  47             unchecked
  48           >::type::template apply<
  49             S,
  50             Pos
  51           >
  52         {};
  53       };
  54     }
  55   }
  56 }
  57
  58 #endif
  59