metaparse/v1/always.hpp

0001 #ifndef BOOST_METAPARSE_V1_ALWAYS_HPP
0002 #define BOOST_METAPARSE_V1_ALWAYS_HPP
0003
0004 // Copyright Abel Sinkovics (abel@sinkovics.hu)  2009 - 2010.
0005 // Distributed under the Boost Software License, Version 1.0.
0006 //    (See accompanying file LICENSE_1_0.txt or copy at
0007 //          http://www.boost.org/LICENSE_1_0.txt)
0008
0009 #include <boost/metaparse/v1/accept.hpp>
0010 #include <boost/metaparse/v1/is_error.hpp>
0011 #include <boost/metaparse/v1/get_remaining.hpp>
0012 #include <boost/metaparse/v1/get_position.hpp>
0013
0014 #include <boost/mpl/eval_if.hpp>
0015
0016 namespace boost
0017 {
0018   namespace metaparse
0019   {
0020     namespace v1
0021     {
0022       template <class P, class Result>
0023       struct always
0024       {
0025       private:
0026         template <class Res>
0027         struct apply_unchecked :
0028           accept<
0029             Result,
0030             typename get_remaining<Res>::type,
0031             typename get_position<Res>::type
0032           >
0033         {};
0034       public:
0035         typedef always type;
0036
0037         template <class S, class Pos>
0038         struct apply :
0039           boost::mpl::eval_if<
0040             typename is_error<typename P::template apply<S, Pos> >::type,
0041             typename P::template apply<S, Pos>,
0042             apply_unchecked<typename P::template apply<S, Pos> >
0043           >
0044         {};
0045       };
0046     }
0047   }
0048 }
0049
0050 #endif
0051