slogo

Class SLogoInterpreter

java.lang.Object

slogo.SLogoInterpreter

public class SLogoInterpreter
extends java.lang.Object

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

See Also:

slogo.expression, slogo.instruction, InstructionParser

Field Summary

Fields

Modifier and Type	Field and Description
private Token	myToken
private java.io.StreamTokenizer	myTokenizer
private java.io.PrintStream	outAndErrStream
private TurtleField	turtleField

Constructor Summary

Constructors

Constructor and Description
SLogoInterpreter(java.io.PrintStream outAndErrStream, TurtleField turtleField) SlogoInterpreter Constructor

Method Summary

Modifier and Type	Method and Description
void	error(Token t)
Token	getToken() returns the current token, doesn't fetch a new one
TurtleField	getTurtleField() Gets the turtleField so that other tokens can use it
void	initializeTokenizer(java.io.Reader reader)
void	interpret(java.io.Reader reader) interprets the contents of the Reader: parsing expression(s) and prints the result of evaluating the expression(s).
void	interpret(java.io.Reader reader, SLogoTurtle c)
void	interpret(java.io.Reader reader, SLogoTurtle c, boolean printLine)
Token	match(Token rhs) try to match a token, if unsuccessful throw an exception, otherwise match succeeds, and next token is obtained and returned
Token	nextToken() get the next token and store it for retrieval by getToken()

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

outAndErrStream

private java.io.PrintStream outAndErrStream

turtleField

private TurtleField turtleField

Constructor Detail

SLogoInterpreter

public SLogoInterpreter(java.io.PrintStream outAndErrStream,
                        TurtleField turtleField)

SlogoInterpreter Constructor

Method Detail

initializeTokenizer

public void initializeTokenizer(java.io.Reader reader)

Parameters:

reader - is the reader that reads the commands

interpret

public void interpret(java.io.Reader reader)

interprets the contents of the Reader: parsing expression(s) and prints the result of evaluating the expression(s).

Parameters:

reader - the reader that will be tokenized

interpret

public void interpret(java.io.Reader reader,
                      SLogoTurtle c,
                      boolean printLine)

Parameters:

reader - is the Reader that reads the commands

c - is the SlogoTurtle that evaluates the evaluates the commands

interpret

public void interpret(java.io.Reader reader,
                      SLogoTurtle c)

Parameters:

reader - is the Reader that reads the commands

c - is the SlogoTurtle that evaluates the evaluates the commands

nextToken

public 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

getTurtleField

public TurtleField getTurtleField()

Gets the turtleField so that other tokens can use it

Returns:

The turtleField