elan.parser
Class ElanParser

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

public class ElanParser

extends java.lang.Object

A singleton; uses the StreamTokenizer class to parse an input file based on set options.

See Also:

elan.expression, elan.instruction

Field Summary

protected Token	myToken
protected java.io.StreamTokenizer	myTokenizer

Constructor Summary

ElanParser()

Method Summary

void	error(Token t)
int	getCurrentLineNumber() Returns the current line number where the parser is.
static ElanParser	getInstance() returns the ElanParser instance.
java.util.ArrayList	getInstructions() Returns the instructions that are stored while parsing.
Token	getToken()
void	incrementLineNumber() Increments the internal line number counter.
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()
boolean	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 Token myToken

Constructor Detail

ElanParser

public ElanParser()

Method Detail

getInstance

public static ElanParser getInstance()

returns the ElanParser instance.

parse

public boolean 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 Token nextToken()

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

Returns:

the current (just read) token

See Also:

getToken

getToken

public Token getToken()

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

getInstructions

public java.util.ArrayList getInstructions()

Returns the instructions that are stored while parsing.

getCurrentLineNumber

public int getCurrentLineNumber()

Returns the current line number where the parser is.

incrementLineNumber

public void incrementLineNumber()

Increments the internal line number counter.