edu.jmu.decaf

Class DecafParser

java.lang.Object

edu.jmu.decaf.DecafParser

Direct Known Subclasses:

MyDecafParser

public abstract class DecafParser
extends Object

"Stub" Decaf parser. Contains utility methods useful for manipulating token lists.

Constructor Summary

Constructors

Constructor and Description
DecafParser()

Method Summary

Modifier and Type	Method and Description
void	consumeNextToken(Queue<Token> tokens) Discard the next token.
SourceInfo	getCurrentSourceInfo(Queue<Token> tokens) Retrieve the source info associated with the token at the head of the queue.
boolean	isNextToken(Queue<Token> tokens, Token.Type type) Returns true if and only if the head of the queue is a token of the expected type.
boolean	isNextTokenKeyword(Queue<Token> tokens, String keyword) Returns true if and only if the head of the queue is a keyword token with the expected text.
boolean	isNextTokenSymbol(Queue<Token> tokens, String symbol) Returns true if and only if the head of the queue is a symbol token with the expected text.
void	matchKeyword(Queue<Token> tokens, String keyword) Match and discard the given keyword from the head of the token queue.
void	matchSymbol(Queue<Token> tokens, String symbol) Match and discard the given symbol from the head of the token queue.
ASTProgram	parse(Queue<Token> tokens) Perform syntax analysis, converting a stream of Token objects into an ASTProgram.

Methods inherited from class java.lang.Object

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

Constructor Detail

DecafParser

public DecafParser()

Method Detail

parse

public ASTProgram parse(Queue<Token> tokens)
                 throws InvalidSyntaxException

Perform syntax analysis, converting a stream of Token objects into an ASTProgram.

Parameters:

tokens - Input token queue

Returns:

Parsed abstract syntax tree (AST)

Throws:

InvalidSyntaxException - Thrown if a syntax error is encountered

matchSymbol

public void matchSymbol(Queue<Token> tokens,
                        String symbol)
                 throws InvalidSyntaxException

Match and discard the given symbol from the head of the token queue. If the token is not present, it throws an exception. This is intended for use in LL(1) parsing routines.

Parameters:

tokens - Input token queue

symbol - Expected symbol text

Throws:

InvalidSyntaxException - Thrown if the queue is empty or the token does not match

matchKeyword

public void matchKeyword(Queue<Token> tokens,
                         String keyword)
                  throws InvalidSyntaxException

Match and discard the given keyword from the head of the token queue. If the token is not present, it throws an exception. This is intended for use in LL(1) parsing routines.

Parameters:

tokens - Input token queue

keyword - Expected keyword text

Throws:

InvalidSyntaxException - Thrown if the queue is empty or the token does not match

isNextToken

public boolean isNextToken(Queue<Token> tokens,
                           Token.Type type)

Returns true if and only if the head of the queue is a token of the expected type.

Parameters:

tokens - Input token queue

type - Expected token type

Returns:

Boolean indicating whether the next token matches

isNextTokenSymbol

public boolean isNextTokenSymbol(Queue<Token> tokens,
                                 String symbol)

Returns true if and only if the head of the queue is a symbol token with the expected text.

Parameters:

tokens - Input token queue

symbol - Expected symbol text

Returns:

Boolean indicating whether the next token matches

isNextTokenKeyword

public boolean isNextTokenKeyword(Queue<Token> tokens,
                                  String keyword)

Returns true if and only if the head of the queue is a keyword token with the expected text.

Parameters:

tokens - Input token queue

keyword - Expected keyword text

Returns:

Boolean indicating whether the next token matches

consumeNextToken

public void consumeNextToken(Queue<Token> tokens)
                      throws InvalidSyntaxException

Discard the next token. Throws an exception if the queue is empty.

Parameters:

tokens - Input token queue

Throws:

InvalidSyntaxException - Thrown if the queue is empty

getCurrentSourceInfo

public SourceInfo getCurrentSourceInfo(Queue<Token> tokens)

Retrieve the source info associated with the token at the head of the queue. If the queue is empty, it returns the INVALID constant.

Parameters:

tokens - Input token queue

Returns:

Source info for the head of the queue