slogo.jelan.parser
Class ElanParser

java.lang.Object
  slogo.jelan.parser.ElanParser

public class ElanParser
extends java.lang.Object

Illustrates the java.io.StreamTokenizer class and how it can be used to parse tokens for a toy example programming language (elan). For this example simple instructions are parsed, but lots of infrastructure is in place for parsing a more complete language.

Author:

Owen Astrachan

See Also:

slogo.jelan.expressions, slogo.jelan.instructions, InstructionParser

Constructor Summary

ElanParser()

Method Summary

void	error(Token t)
Token	getToken() returns the current token, doesn't fetch a new one
static void	main(java.lang.String[] args) Basic driver for ElanParser
Token	match(Token rhs) try to match a token, if unsuccessful throw an exception, otherwise match succeeds, and next token is obtained and returned
void	parse(java.io.Reader r) parses an expression and prints the result of evaluating the expression.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ElanParser

public ElanParser()

Method Detail

parse

public void parse(java.io.Reader r)

parses an expression and prints the result of evaluating the expression.

Parameters:

r - the reader that will be tokenized

getToken

public Token getToken()

returns the current token, doesn't fetch a new one

Returns:

the current token

match

public Token match(Token rhs)

try to match a token, if unsuccessful throw an exception, otherwise match succeeds, and next token is obtained and returned

Parameters:

rhs - token being matched

Returns:

the next read token

Throws:

ParseException - if match fails

error

public void error(Token t)

Parameters:

t - token where error occurred

Throws:

a - ParseException labeled by t

main

public static void main(java.lang.String[] args)

Basic driver for ElanParser

Parameters:

args -