elan.parser
Class ElanParser

java.lang.Object
  |
  +--elan.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 only expressions are parsed, but lots of infrastructure is in place for parsing a more complete language

See Also:

elan.expression, elan.instruction

Field Summary

protected elan.parser.token.Token	myToken
protected java.io.StreamTokenizer	myTokenizer

Constructor Summary

ElanParser()

Method Summary

void	error(elan.parser.token.Token t)
elan.parser.token.Token	getToken()
static void	main(java.lang.String[] args)
elan.parser.token.Token	match(elan.parser.token.Token rhs) try to match a token, if unsuccessful throw an exception, otherwise match succeeds, and next token is obtained and returned
protected elan.parser.token.Token	nextToken() get the next token and store it for retrieval by getToken()
void	parse(java.io.Reader r) parses an expression and prints the result of evaluating the expression.
protected void	skipLines() skip EOL tokens, the next call of getToken() returns something other than EOLToken

Methods inherited from class java.lang.Object

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

Field Detail

myTokenizer

protected java.io.StreamTokenizer myTokenizer

myToken

protected elan.parser.token.Token myToken

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 - is the reader that will be tokenized

skipLines

protected void skipLines()

skip EOL tokens, the next call of getToken() returns something other than EOLToken

nextToken

protected elan.parser.token.Token nextToken()

get the next token and store it for retrieval by getToken()

Returns:

the current (just read) token

See Also:

getToken

getToken

public elan.parser.token.Token getToken()

Returns:

the current token

match

public elan.parser.token.Token match(elan.parser.token.Token rhs)

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

Parameters:

rhs - is the token being matched

Returns:

the next read token

Throws:

ParseException - (RunTime) if match fails

error

public void error(elan.parser.token.Token t)

Parameters:

t - is included in expeption thrown

Throws:

a - ParseException labelled by t

main

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