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

   1 #ifndef BOOST_METAPARSE_V1_LOOK_AHEAD_HPP
   2 #define BOOST_METAPARSE_V1_LOOK_AHEAD_HPP
   3
   4 // Copyright Abel Sinkovics (abel@sinkovics.hu)   2011.
   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/is_error.hpp>
  10 #include <boost/metaparse/v1/accept.hpp>
  11 #include <boost/metaparse/v1/get_result.hpp>
  12
  13 #include <boost/mpl/eval_if.hpp>
  14
  15 namespace boost
  16 {
  17   namespace metaparse
  18   {
  19     namespace v1
  20     {
  21       template <class P>
  22       struct look_ahead
  23       {
  24       private:
  25         template <class S, class Pos>
  26         struct no_error :
  27           accept<
  28             typename get_result<typename P::template apply<S, Pos> >::type,
  29             S,
  30             Pos
  31           >
  32         {};
  33       public:
  34         typedef look_ahead type;
  35
  36         template <class S, class Pos>
  37         struct apply :
  38           boost::mpl::eval_if<
  39             typename is_error<typename P::template apply<S, Pos> >::type,
  40             typename P::template apply<S, Pos>,
  41             no_error<S, Pos>
  42           >
  43         {};
  44       };
  45     }
  46   }
  47 }
  48
  49 #endif
  50