slogo.parser

Class SLogoParser

java.lang.Object

slogo.parser.SLogoParser

public class SLogoParser
extends java.lang.Object

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

See Also:

slogo.expression, slogo.instruction, InstructionParser

Field Summary

Fields

Modifier and Type	Field and Description
private Context	myContext
private Token	myToken
private java.io.StreamTokenizer	myTokenizer

Constructor Summary

Constructors

Constructor and Description
SLogoParser(Context c)

Method Summary

Methods

Modifier and Type	Method and Description
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 SLogoParser
Token	match(Token rhs) try to match a token, if unsuccessful throw an exception, otherwise match succeeds, and next token is obtained and returned
protected 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.

Methods inherited from class java.lang.Object

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

Field Detail

myTokenizer

private java.io.StreamTokenizer myTokenizer

myToken

private Token myToken

myContext

private Context myContext

Constructor Detail

SLogoParser

public SLogoParser(Context c)

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

nextToken

protected Token nextToken()

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

Returns:

the current (just read) token

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 SLogoParser

Parameters:

args -