Parser Struct Template Reference
[Series]

Parser class used in the parse() function. More...

List of all members.

Public Types
typedef KRatExpToken< typename Element< S, T >::monoid_elt_value_t, typename Element< S, T >::semiring_elt_value_t >	krat_exp_token_t
typedef Element< S, T >::monoid_elt_t	monoid_elt_t
typedef Element< S, T >::monoid_elt_value_t	monoid_elt_value_t
typedef monoid_elt_t::set_t	monoid_t
typedef Element< S, T >::semiring_elt_t	semiring_elt_t
typedef semiring_elt_t::set_t	semiring_t
typedef Element< S, T >::semiring_elt_value_t	semiring_elt_value_t
typedef std::list< krat_exp_token_t >	token_stream_t
Public Member Functions
	Parser (Lexer< S, T > &lexer, bool trace=false)
void	parse (Element< S, T > &exp)
	Do the parsing.
bool	error () const
	Return true when an error occured.
const std::string &	error_msg () const
	Return the error message.
void	set_trace (bool trace)
Protected Member Functions
void	parse_error (const std::string &msg="parse_error.") throw (const std::string&)
	Generate a parse error.
void	accept (token_e tok)
	Accept token, or generate an error.
void	parse_exp (Element< S, T > &exp)
	exp ::= term ('+' term)*
void	parse_term (Element< S, T > &exp)
	term ::= right_weighted ('.'? right_weighted)*
void	parse_right_weighted (Element< S, T > &exp)
	right_weighted ::= left_weighted (' ' weight)*
void	parse_left_weighted (Element< S, T > &exp)
	left_weighted ::= weight ' ' left_weighted | stared
void	parse_stared (Element< S, T > &exp)
	stared ::= factor '*'*
void	parse_factor (Element< S, T > &exp)
	factor ::= 1 | 0 | word | '(' exp ')'
void	trace (const std::string &msg)
	Trace parsing.
template<class Misc>
void	trace (const std::string &msg, const Misc &v)
	Trace parsing.
Protected Attributes
Lexer< S, T > &	lexer_
bool	trace_
bool	error_
std::string	error_msg_

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Detailed Description

template<class S, class T>
struct vcsn::algebra::Parser< S, T >

Parser class used in the parse() function.

This class handles rational expression parsing, once a Lexer has been created.

Ideally, we would like to parse:

     exp ::= '(' exp ')'
         |   exp '+' exp
         |   exp '.' exp
         |   exp exp
         |   exp '*'
         |   weight ' ' exp
         |   exp ' ' weight
         |   0
         |   1
         |   word
     

But this grammar has to be changed to allow a classical LL(2) parsing:

     exp		::= term ('+' term)*
     term		::= right_weighted ('.'? right_weighted)*
     right_weighted	::= left_weighted (' ' weight)*
     left_weighted	::= weight ' ' left_weighted
                        |   stared
     stared		::= factor '*'*
     factor		::= '(' exp ')' | word | 0 | 1
     

Definition at line 420 of file krat_exp_parser.hxx.

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Member Function Documentation

void accept (  token_e  tok  )  [inline, protected]

Accept token, or generate an error. This function asks the lexer whether the first input token matches the argument or not. When matching is successfull, the first input token is eaten, an error is risen else. Parameters: tok  The token to match. Definition at line 517 of file krat_exp_parser.hxx. References KRatExpToken::is_a(), Parser::lexer_, Parser::parse_error(), KRatExpToken::to_string(), and Parser::trace(). Referenced by Parser::parse(), and Parser::parse_exp().

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