what.hpp

来自「Boost provides free peer-reviewed portab」· HPP 代码 · 共 35 行

/*=============================================================================
    Copyright (c) 2001-2007 Joel de Guzman

    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)
=============================================================================*/
#if !defined(BOOST_SPIRIT_WHAT_APRIL_21_2007_0732AM)
#define BOOST_SPIRIT_WHAT_APRIL_21_2007_0732AM

#include <boost/spirit/home/qi/meta_grammar.hpp>
#include <boost/mpl/assert.hpp>
#include <string>

namespace boost { namespace spirit { namespace qi
{
    template <typename Expr>
    inline std::string what(Expr const& xpr)
    {
        typedef spirit::traits::is_component<qi::domain, Expr> is_component;

        // report invalid expression error as early as possible
        BOOST_MPL_ASSERT_MSG(
            is_component::value,
            xpr_is_not_convertible_to_a_parser, ());

        typedef typename result_of::as_component<qi::domain, Expr>::type component;
        typedef typename component::director director;
        component c = spirit::as_component(qi::domain(), xpr);
        return director::what(c, unused);
    }
}}}

#endif