nonterminal/detail/parser_binder.hpp

0001 /*=============================================================================
0002     Copyright (c) 2001-2011 Joel de Guzman
0003
0004     Distributed under the Boost Software License, Version 1.0. (See accompanying
0005     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 ==============================================================================*/
0007 #if !defined(BOOST_SPIRIT_PARSER_BINDER_DECEMBER_05_2008_0516_PM)
0008 #define BOOST_SPIRIT_PARSER_BINDER_DECEMBER_05_2008_0516_PM
0009
0010 #if defined(_MSC_VER)
0011 #pragma once
0012 #endif
0013
0014 #include <boost/fusion/include/at.hpp>
0015 #include <boost/mpl/bool.hpp>
0016 #include <boost/spirit/home/support/has_semantic_action.hpp>
0017
0018 namespace boost { namespace spirit { namespace qi { namespace detail
0019 {
0020     // parser_binder for plain rules
0021     template <typename Parser, typename Auto>
0022     struct parser_binder
0023     {
0024         parser_binder(Parser const& p_)
0025           : p(p_) {}
0026
0027         template <typename Iterator, typename Skipper, typename Context>
0028         bool call(Iterator& first, Iterator const& last
0029           , Context& context, Skipper const& skipper, mpl::true_) const
0030         {
0031             // If DeducedAuto is false (semantic actions is present), the
0032             // component's attribute is unused.
0033             return p.parse(first, last, context, skipper, unused);
0034         }
0035
0036         template <typename Iterator, typename Skipper, typename Context>
0037         bool call(Iterator& first, Iterator const& last
0038           , Context& context, Skipper const& skipper, mpl::false_) const
0039         {
0040             // If DeducedAuto is true (no semantic action), we pass the rule's
0041             // attribute on to the component.
0042             return p.parse(first, last, context, skipper
0043                 , fusion::at_c<0>(context.attributes));
0044         }
0045
0046         template <typename Iterator, typename Skipper, typename Context>
0047         bool operator()(
0048             Iterator& first, Iterator const& last
0049           , Context& context, Skipper const& skipper) const
0050         {
0051             // If Auto is false, we need to deduce whether to apply auto rule
0052             typedef typename traits::has_semantic_action<Parser>::type auto_rule;
0053             return call(first, last, context, skipper, auto_rule());
0054         }
0055
0056         Parser p;
0057     };
0058
0059     // parser_binder for auto rules
0060     template <typename Parser>
0061     struct parser_binder<Parser, mpl::true_>
0062     {
0063         parser_binder(Parser const& p_)
0064           : p(p_) {}
0065
0066         template <typename Iterator, typename Skipper, typename Context>
0067         bool operator()(
0068             Iterator& first, Iterator const& last
0069           , Context& context, Skipper const& skipper) const
0070         {
0071             // If Auto is true, we pass the rule's attribute on to the component.
0072             return p.parse(first, last, context, skipper
0073                 , fusion::at_c<0>(context.attributes));
0074         }
0075
0076         Parser p;
0077     };
0078
0079     template <typename Auto, typename Parser>
0080     inline parser_binder<Parser, Auto>
0081     bind_parser(Parser const& p)
0082     {
0083         return parser_binder<Parser, Auto>(p);
0084     }
0085 }}}}
0086
0087 #endif