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>
