elan.parser
Class ElanParser

java.lang.Object
  |
  +--elan.parser.ElanParser

All Implemented Interfaces:

Parser

public class ElanParser

extends java.lang.Object

implements Parser

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.

See Also:

elan.expression, elan.instruction, InstructionParser

Field Summary

protected Output	myOutput
protected Token	myToken
protected java.io.StreamTokenizer	myTokenizer
protected TurtleManager	myTurtleManager

Constructor Summary

ElanParser()

Method Summary

void	error(Token t)
void	executeInstructions(java.lang.String instructionList) executes a list of instructions
Token	getToken() returns the current token, doesn't fetch a new one
static void	main(java.lang.String[] args)
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.
void	setOutput()
void	setOutput(Output o) Deprecated. The current version of ElanParser treats EOL (end-of-line) as NOT significant, so there's no reason to call this function.
void	setTurtleManager()
void	setTurtleManager(TurtleManager t)
protected void	skipLines()

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 Token myToken

myOutput

protected Output myOutput

myTurtleManager

protected TurtleManager myTurtleManager

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

setOutput

public void setOutput(Output o)

Deprecated. The current version of ElanParser treats EOL (end-of-line) as NOT significant, so there's no reason to call this function.

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

setTurtleManager

public void setTurtleManager(TurtleManager t)

skipLines

protected void skipLines()

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 - is the token being matched

Returns:

the next read token

Throws:

ParseException - (RunTime) if match fails

error

public void error(Token t)

Parameters:

t - is included in expeption thrown

Throws:

a - ParseException labelled by t

executeInstructions

public void executeInstructions(java.lang.String instructionList)

Description copied from interface: Parser

executes a list of instructions

Specified by:

executeInstructions in interface Parser

Following copied from interface: graphics.Parser

Parameters:

instructionList - instructions that can be interpreted and executed by the parser

setTurtleManager

public void setTurtleManager()

setOutput

public void setOutput()

main

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