Chris@16: /*=============================================================================
Chris@16:     Copyright (c) 2002-2003 Joel de Guzman
Chris@16:     Copyright (c) 2002 Juan Carlos Arevalo-Baeza
Chris@16:     Copyright (c) 2002-2003 Martin Wille
Chris@16:     http://spirit.sourceforge.net/
Chris@16: 
Chris@16:   Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16:   file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: =============================================================================*/
Chris@16: #ifndef BOOST_SPIRIT_IF_HPP
Chris@16: #define BOOST_SPIRIT_IF_HPP
Chris@16: 
Chris@16: #include <boost/spirit/home/classic/namespace.hpp>
Chris@16: #include <boost/spirit/home/classic/core/parser.hpp>
Chris@16: #include <boost/spirit/home/classic/core/composite/composite.hpp>
Chris@16: #include <boost/spirit/home/classic/dynamic/impl/conditions.ipp>
Chris@16: 
Chris@16: namespace boost { namespace spirit {
Chris@16: 
Chris@16: BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN
Chris@16: 
Chris@16:     namespace impl {
Chris@16: 
Chris@16:     //////////////////////////////////
Chris@16:     // if-else-parser, holds two alternative parsers and a conditional functor
Chris@16:     // that selects between them.
Chris@16:     template <typename ParsableTrueT, typename ParsableFalseT, typename CondT>
Chris@16:     struct if_else_parser
Chris@16:         : public condition_evaluator<typename as_parser<CondT>::type>
Chris@16:         , public binary
Chris@16:         <
Chris@16:             typename as_parser<ParsableTrueT>::type,
Chris@16:             typename as_parser<ParsableFalseT>::type,
Chris@16:             parser< if_else_parser<ParsableTrueT, ParsableFalseT, CondT> >
Chris@16:         >
Chris@16:     {
Chris@16:         typedef if_else_parser<ParsableTrueT, ParsableFalseT, CondT>  self_t;
Chris@16: 
Chris@16:         typedef as_parser<ParsableTrueT>            as_parser_true_t;
Chris@16:         typedef as_parser<ParsableFalseT>           as_parser_false_t;
Chris@16:         typedef typename as_parser_true_t::type     parser_true_t;
Chris@16:         typedef typename as_parser_false_t::type    parser_false_t;
Chris@16:         typedef as_parser<CondT>                    cond_as_parser_t;
Chris@16:         typedef typename cond_as_parser_t::type     condition_t;
Chris@16: 
Chris@16:         typedef binary<parser_true_t, parser_false_t, parser<self_t> > base_t;
Chris@16:         typedef condition_evaluator<condition_t>                       eval_t;
Chris@16: 
Chris@16:         if_else_parser
Chris@16:         (
Chris@16:             ParsableTrueT  const& p_true,
Chris@16:             ParsableFalseT const& p_false,
Chris@16:             CondT          const& cond_
Chris@16:         )
Chris@16:             : eval_t(cond_as_parser_t::convert(cond_))
Chris@16:             , base_t
Chris@16:                 (
Chris@16:                     as_parser_true_t::convert(p_true),
Chris@16:                     as_parser_false_t::convert(p_false)
Chris@16:                 )
Chris@16:         { }
Chris@16: 
Chris@16:         template <typename ScannerT>
Chris@16:         struct result
Chris@16:         {
Chris@16:             typedef typename match_result<ScannerT, nil_t>::type type;
Chris@16:         };
Chris@16: 
Chris@16:         template <typename ScannerT>
Chris@16:         typename parser_result<self_t, ScannerT>::type
Chris@16:         parse(ScannerT const& scan) const
Chris@16:         {
Chris@16:             typedef typename parser_result
Chris@16:                 <parser_true_t, ScannerT>::type   then_result_t;
Chris@16:             typedef typename parser_result
Chris@16:                 <parser_false_t, ScannerT>::type  else_result_t;
Chris@16: 
Chris@16:             typename ScannerT::iterator_t const  save(scan.first);
Chris@16: 
Chris@16:             std::ptrdiff_t length = this->evaluate(scan);
Chris@16:             if (length >= 0)
Chris@16:             {
Chris@16:                 then_result_t then_result(this->left().parse(scan));
Chris@16:                 if (then_result)
Chris@16:                 {
Chris@16:                     length += then_result.length();
Chris@16:                     return scan.create_match(std::size_t(length), nil_t(), save, scan.first);
Chris@16:                 }
Chris@16:             }
Chris@16:             else
Chris@16:             {
Chris@16:                 else_result_t else_result(this->right().parse(scan));
Chris@16:                 if (else_result)
Chris@16:                 {
Chris@16:                     length = else_result.length();
Chris@16:                     return scan.create_match(std::size_t(length), nil_t(), save, scan.first);
Chris@16:                 }
Chris@16:             }
Chris@16:             return scan.no_match();
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     //////////////////////////////////
Chris@16:     // if-else-parser generator, takes the false-parser in brackets
Chris@16:     // and returns the if-else-parser.
Chris@16:     template <typename ParsableTrueT, typename CondT>
Chris@16:     struct if_else_parser_gen
Chris@16:     {
Chris@16:         if_else_parser_gen(ParsableTrueT const& p_true_, CondT const& cond_)
Chris@16:             : p_true(p_true_)
Chris@16:             , cond(cond_) {}
Chris@16: 
Chris@16:         template <typename ParsableFalseT>
Chris@16:         if_else_parser
Chris@16:         <
Chris@16:             ParsableTrueT,
Chris@16:             ParsableFalseT,
Chris@16:             CondT
Chris@16:         >
Chris@16:         operator[](ParsableFalseT const& p_false) const
Chris@16:         {
Chris@16:             return if_else_parser<ParsableTrueT, ParsableFalseT, CondT>
Chris@16:                 (
Chris@16:                     p_true,
Chris@16:                     p_false,
Chris@16:                     cond
Chris@16:                 );
Chris@16:         }
Chris@16: 
Chris@16:         ParsableTrueT const &p_true;
Chris@16:         CondT const &cond;
Chris@16:     };
Chris@16: 
Chris@16:     //////////////////////////////////
Chris@16:     // if-parser, conditionally runs a parser is a functor condition is true.
Chris@16:     // If the condition is fales, it fails the parse.
Chris@16:     // It can optionally become an if-else-parser through the member else_p.
Chris@16:     template <typename ParsableT, typename CondT>
Chris@16:     struct if_parser
Chris@16:         : public condition_evaluator<typename as_parser<CondT>::type>
Chris@16:         , public unary
Chris@16:         <
Chris@16:             typename as_parser<ParsableT>::type,
Chris@16:             parser<if_parser<ParsableT, CondT> > >
Chris@16:     {
Chris@16:         typedef if_parser<ParsableT, CondT>           self_t;
Chris@16:         typedef as_parser<ParsableT>                  as_parser_t;
Chris@16:         typedef typename as_parser_t::type            parser_t;
Chris@16: 
Chris@16:         typedef as_parser<CondT>                      cond_as_parser_t;
Chris@16:         typedef typename cond_as_parser_t::type       condition_t;
Chris@16:         typedef condition_evaluator<condition_t>      eval_t;
Chris@16:         typedef unary<parser_t, parser<self_t> >      base_t;
Chris@16: 
Chris@16:         if_parser(ParsableT const& p, CondT const& cond_)
Chris@16:             : eval_t(cond_as_parser_t::convert(cond_))
Chris@16:             , base_t(as_parser_t::convert(p))
Chris@16:             , else_p(p, cond_)
Chris@16:         {}
Chris@16: 
Chris@16:         template <typename ScannerT>
Chris@16:         struct result
Chris@16:         {
Chris@16:             typedef typename match_result<ScannerT, nil_t>::type type;
Chris@16:         };
Chris@16: 
Chris@16:         template <typename ScannerT>
Chris@16:         typename parser_result<self_t, ScannerT>::type
Chris@16:         parse(ScannerT const& scan) const
Chris@16:         {
Chris@16:             typedef typename parser_result<parser_t, ScannerT>::type t_result_t;
Chris@16:             typename ScannerT::iterator_t const save(scan.first);
Chris@16: 
Chris@16:             std::ptrdiff_t length = this->evaluate(scan);
Chris@16:             if (length >= 0)
Chris@16:             {
Chris@16:                 t_result_t then_result(this->subject().parse(scan));
Chris@16:                 if (then_result)
Chris@16:                 {
Chris@16:                     length += then_result.length();
Chris@16:                     return scan.create_match(std::size_t(length), nil_t(), save, scan.first);
Chris@16:                 }
Chris@16:                 return scan.no_match();
Chris@16:             }
Chris@16:             return scan.empty_match();
Chris@16:         }
Chris@16: 
Chris@16:         if_else_parser_gen<ParsableT, CondT> else_p;
Chris@16:     };
Chris@16: 
Chris@16:     //////////////////////////////////
Chris@16:     // if-parser generator, takes the true-parser in brackets and returns the
Chris@16:     // if-parser.
Chris@16:     template <typename CondT>
Chris@16:     struct if_parser_gen
Chris@16:     {
Chris@16:         if_parser_gen(CondT const& cond_) : cond(cond_) {}
Chris@16: 
Chris@16:         template <typename ParsableT>
Chris@16:         if_parser
Chris@16:         <
Chris@16:             ParsableT,
Chris@16:             CondT
Chris@16:         >
Chris@16:         operator[](ParsableT const& subject) const
Chris@16:         {
Chris@16:             return if_parser<ParsableT, CondT>(subject, cond);
Chris@16:         }
Chris@16: 
Chris@16:         CondT const &cond;
Chris@16:     };
Chris@16: 
Chris@16: } // namespace impl
Chris@16: 
Chris@16: //////////////////////////////////
Chris@16: // if_p function, returns "if" parser generator
Chris@16: 
Chris@16: template <typename CondT>
Chris@16: impl::if_parser_gen<CondT>
Chris@16: if_p(CondT const& cond)
Chris@16: {
Chris@16:     return impl::if_parser_gen<CondT>(cond);
Chris@16: }
Chris@16: 
Chris@16: BOOST_SPIRIT_CLASSIC_NAMESPACE_END
Chris@16: 
Chris@16: }} // namespace BOOST_SPIRIT_CLASSIC_NS
Chris@16: 
Chris@16: #endif // BOOST_SPIRIT_IF_HPP