net.percederberg.grammatica.parser
Class RecursiveDescentParser

java.lang.Object
  net.percederberg.grammatica.parser.Parser
      net.percederberg.grammatica.parser.RecursiveDescentParser

public class RecursiveDescentParser
extends Parser

A recursive descent parser. This parser handles LL(n) grammars, selecting the appropriate pattern to parse based on the next few tokens. The parser is more efficient the fewer look-ahead tokens that is has to consider.

Constructor Summary

RecursiveDescentParser(java.io.Reader input)
Creates a new parser.

RecursiveDescentParser(java.io.Reader input, Analyzer analyzer)
Creates a new parser.

RecursiveDescentParser(Tokenizer tokenizer)
Creates a new parser.

RecursiveDescentParser(Tokenizer tokenizer, Analyzer analyzer)
Creates a new parser.

Method Summary

void	addPattern(ProductionPattern pattern) Adds a new production pattern to the parser.
protected Node	parseStart() Parses the input stream and creates a parse tree.
void	prepare() Initializes the parser.

Methods inherited from class net.percederberg.grammatica.parser.Parser

getAnalyzer, getTokenizer, newAnalyzer, newProduction, newTokenizer, parse, reset, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

RecursiveDescentParser

public RecursiveDescentParser(java.io.Reader input)
                       throws ParserCreationException

Creates a new parser.

Parameters:

input - the input stream to read from

Throws:

ParserCreationException - if the tokenizer couldn't be initialized correctly

Since:

1.5

RecursiveDescentParser

public RecursiveDescentParser(java.io.Reader input,
                              Analyzer analyzer)
                       throws ParserCreationException

Creates a new parser.

Parameters:

input - the input stream to read from

analyzer - the analyzer callback to use

Throws:

ParserCreationException - if the tokenizer couldn't be initialized correctly

Since:

1.5

RecursiveDescentParser

public RecursiveDescentParser(Tokenizer tokenizer)

Creates a new parser.

Parameters:

tokenizer - the tokenizer to use

RecursiveDescentParser

public RecursiveDescentParser(Tokenizer tokenizer,
                              Analyzer analyzer)

Creates a new parser.

Parameters:

tokenizer - the tokenizer to use

analyzer - the analyzer callback to use

Method Detail

addPattern

public void addPattern(ProductionPattern pattern)
                throws ParserCreationException

Adds a new production pattern to the parser. The pattern will be added last in the list. The first pattern added is assumed to be the starting point in the grammar. The pattern will be validated against the grammar type to some extent.

Overrides:

addPattern in class Parser

Parameters:

pattern - the pattern to add

Throws:

ParserCreationException - if the pattern couldn't be added correctly to the parser

prepare

public void prepare()
             throws ParserCreationException

Initializes the parser. All the added production patterns will be analyzed for ambiguities and errors. This method also initializes the internal data structures used during the parsing.

Overrides:

prepare in class Parser

Throws:

ParserCreationException - if the parser couldn't be initialized correctly

parseStart

protected Node parseStart()
                   throws ParseException

Parses the input stream and creates a parse tree.

Specified by:

parseStart in class Parser

Returns:

the parse tree

Throws:

ParseException - if the input couldn't be parsed correctly