alternative_function.hpp

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/*=============================================================================
    Copyright (c) 2001-2008 Hartmut Kaiser

    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(SPIRIT_ALTERNATIVE_FUNCTION_APR_23_2007_1046AM)
#define SPIRIT_ALTERNATIVE_FUNCTION_APR_23_2007_1046AM

#include <boost/spirit/home/qi/domain.hpp>
#include <boost/spirit/home/support/unused.hpp>
#include <boost/spirit/home/support/attribute_of.hpp>
#include <boost/variant.hpp>

namespace boost { namespace spirit { namespace qi { namespace detail
{
    template <typename Iterator, typename Context, typename Skipper,
        typename Attribute>
    struct alternative_function
    {
        alternative_function(
            Iterator& first, Iterator const& last, Context& context,
            Skipper const& skipper, Attribute& attr)
          : first(first), last(last), context(context), skipper(skipper),
            attr(attr)
        {
        }

        template <typename Component>
        bool operator()(Component const& component)
        {
            // return true if the parser succeeds
            typedef typename Component::director director;
            typename
                traits::attribute_of<
                    qi::domain, Component, Context, Iterator>::type
            val;

            if (director::parse(component, first, last, context, skipper, val))
            {
                attr = val;
                return true;
            }
            return false;
        }

        Iterator& first;
        Iterator const& last;
        Context& context;
        Skipper const& skipper;
        Attribute& attr;
    };

    template <typename Iterator, typename Context, typename Skipper>
    struct alternative_function<Iterator, Context, Skipper, unused_type const>
    {
        alternative_function(
            Iterator& first, Iterator const& last, Context& context,
            Skipper const& skipper, unused_type)
          : first(first), last(last), context(context), skipper(skipper)
        {
        }

        template <typename Component>
        bool operator()(Component const& component)
        {
            // return true if the parser succeeds
            typedef typename Component::director director;
            return director::parse(component, first, last, context, skipper,
                unused);
        }

        Iterator& first;
        Iterator const& last;
        Context& context;
        Skipper const& skipper;
    };

}}}}

#endif