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boost/spirit/core/parser.hpp

/*=============================================================================
    Copyright (c) 1998-2003 Joel de Guzman
    http://spirit.sourceforge.net/

    Use, modification and distribution is subject to 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_PARSER_HPP)
#define BOOST_SPIRIT_PARSER_HPP

#include <boost/config.hpp>
#include <boost/type_traits.hpp>
#include <boost/spirit/core/scanner/scanner.hpp>
#include <boost/spirit/core/nil.hpp>

namespace boost { namespace spirit
{
    template <typename ParserT, typename ActionT>
    class action; //  forward declaration

    ///////////////////////////////////////////////////////////////////////////
    //
    //  Parser categories
    //
    //      Helper template classes to distinguish different types of
    //      parsers. The following categories are the most generic. More
    //      specific types may inherit from these. Each parser has a typedef
    //      parser_category_t that defines its category. By default, if one
    //      is not specified, it will inherit from the base parser class
    //      which typedefs its parser_category_t as plain_parser_category.
    //
    //          - plain parser has nothing special
    //          - binary parser has subject a and b (e.g. alternative)
    //          - unary parser has single subject  (e.g. kleene star)
    //          - action parser has an attached action parser
    //
    ///////////////////////////////////////////////////////////////////////////
    struct plain_parser_category {};
    struct binary_parser_category       : plain_parser_category {};
    struct unary_parser_category        : plain_parser_category {};
    struct action_parser_category       : unary_parser_category {};

    ///////////////////////////////////////////////////////////////////////////
    //
    //  parser_result metafunction
    //
    //      Given a scanner type ScannerT and a parser type ParserT, the
    //      parser_result metafunction provides the actual result of the
    //      parser.
    //
    //  Usage:
    //
    //      typename parser_result<ParserT, ScannerT>::type
    //
    ///////////////////////////////////////////////////////////////////////////
    template <typename ParserT, typename ScannerT>
    struct parser_result
    {
        typedef typename boost::remove_reference<ParserT>::type parser_type;
        typedef typename parser_type::template result<ScannerT>::type type;
    };

    ///////////////////////////////////////////////////////////////////////////
    //
    //  parser class
    //
    //      This class is a protocol base class for all parsers. This is
    //      essentially an interface contract. The parser class does not
    //      really know how to parse anything but instead relies on the
    //      template parameter DerivedT (which obviously is assumed to be a
    //      subclass) to do the actual parsing.
    //
    //      Concrete sub-classes inheriting from parser must have a
    //      corresponding member function parse(...) compatible with the
    //      conceptual Interface:
    //
    //          template <typename ScannerT>
    //          RT parse(ScannerT const& scan) const;
    //
    //      where RT is the desired return type of the parser and ScannerT
    //      scan is the scanner (see scanner.hpp).
    //
    //      Concrete sub-classes inheriting from parser in most cases need to
    //      have a nested meta-function result that returns the result type
    //      of the parser's parse member function, given a scanner type. The
    //      meta-function has the form:
    //
    //          template <typename ScannerT>
    //          struct result
    //          {
    //              typedef RT type;
    //          };
    //
    //      where RT is the desired return type of the parser. This is
    //      usually, but not always, dependent on the template parameter
    //      ScannerT. If a parser does not supply a result metafunction, a
    //      default is provided by the base parser class.
    //
    //      The parser's derived() member function returns a reference to the
    //      parser as its derived object.
    //
    //      An operator[] is provided. The operator returns a semantic action
    //      handler (see actions.hpp).
    //
    //      Each parser has a typedef embed_t. This typedef specifies how a
    //      parser is embedded in a composite (see composite.hpp). By
    //      default, if one is not specified, the parser will be embedded by
    //      value. That is, a copy of the parser is placed as a member
    //      variable of the composite. Most parsers are embedded by value. In
    //      certain situations however, this is not desirable or possible.
    //
    ///////////////////////////////////////////////////////////////////////////
    template <typename DerivedT>
    struct parser
    {
        typedef DerivedT                embed_t;
        typedef DerivedT                derived_t;
        typedef plain_parser_category   parser_category_t;

        template <typename ScannerT>
        struct result
        {
            typedef typename match_result<ScannerT, nil_t>::type type;
        };

        DerivedT& derived()
        {
            return *static_cast<DerivedT*>(this);
        }

        DerivedT const& derived() const
        {
            return *static_cast<DerivedT const*>(this);
        }

        template <typename ActionT>
        action<DerivedT, ActionT>
        operator[](ActionT const& actor) const
        {
            return action<DerivedT, ActionT>(derived(), actor);
        }
    };

    ///////////////////////////////////////////////////////////////////////////
    //
    //  parse_info
    //
    //      Results returned by the free parse functions:
    //
    //      stop:   points to the final parse position (i.e parsing
    //              processed the input up to this point).
    //
    //      hit:    true if parsing is successful. This may be full:
    //              the parser consumed all the input, or partial:
    //              the parser consumed only a portion of the input.
    //
    //      full:   true when we have a full hit (i.e the parser
    //              consumed all the input.
    //
    //      length: The number of characters consumed by the parser.
    //              This is valid only if we have a successful hit
    //              (either partial or full).
    //
    ///////////////////////////////////////////////////////////////////////////
    template <typename IteratorT = char const*>
    struct parse_info
    {
        IteratorT   stop;
        bool        hit;
        bool        full;
        std::size_t length;

        parse_info(
            IteratorT const& stop_ = IteratorT(),
            bool hit_ = false,
            bool full_ = false,
            std::size_t length_ = 0)
        : stop(stop_)
        , hit(hit_)
        , full(full_)
        , length(length_) {}

        template <typename ParseInfoT>
        parse_info(ParseInfoT const& pi)
        : stop(pi.stop)
        , hit(pi.hit)
        , full(pi.full)
        , length(pi.length) {}
    };

    ///////////////////////////////////////////////////////////////////////////
    //
    //  Generic parse function
    //
    ///////////////////////////////////////////////////////////////////////////
    template <typename IteratorT, typename DerivedT>
    parse_info<IteratorT>
    parse(
        IteratorT const&        first,
        IteratorT const&        last,
        parser<DerivedT> const& p);

    ///////////////////////////////////////////////////////////////////////////
    //
    //  Parse function for null terminated strings
    //
    ///////////////////////////////////////////////////////////////////////////
    template <typename CharT, typename DerivedT>
    parse_info<CharT const*>
    parse(
        CharT const*            str,
        parser<DerivedT> const& p);

}} // namespace boost::spirit

#endif

#include <boost/spirit/core/impl/parser.ipp>