as_matcher.hpp

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///////////////////////////////////////////////////////////////////////////////
// as_matcher.hpp
//
//  Copyright 2008 Eric Niebler. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_MATCHER_HPP_EAN_04_01_2007
#define BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_MATCHER_HPP_EAN_04_01_2007

// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif

#include <boost/mpl/assert.hpp>
#include <boost/xpressive/detail/detail_fwd.hpp>
#include <boost/xpressive/detail/static/static.hpp>

namespace boost { namespace xpressive { namespace grammar_detail
{
    struct as_matcher : proto::callable
    {
        template<typename Sig> struct result {};

        template<typename This, typename Expr, typename State, typename Visitor>
        struct result<This(Expr, State, Visitor)>
        {
            typedef
                typename Visitor::template apply<
                    typename proto::result_of::arg<Expr>::type
                >::type
            type;
        };

        template<typename Expr, typename State, typename Visitor>
        typename result<void(Expr, State, Visitor)>::type
        operator ()(Expr const &expr, State const &, Visitor &visitor) const
        {
            return visitor.call(proto::arg(expr));
        }
    };

}}}

#endif