Class Parser

java.lang.Object

Parser

public class Parser
extends Object

Recursive descent parser for the YaLCC language. Constructs a parse tree based on the provided lexical analyzer. Each parsing method corresponds to a grammar production.

Field Summary

Fields

Modifier and Type	Field	Description
private Symbol	currentToken	The current token being analyzed
private final LexicalAnalyzer	lexer	The lexical analyzer providing tokens for parsing.

Constructor Summary

Constructors

Constructor	Description
Parser(LexicalAnalyzer lexer)	Creates a parser with the given lexical analyzer.

Method Summary

Modifier and Type	Method	Description
private Symbol	dummy(NonTerminal nt)	Creates a dummy symbol for non-terminal nodes in the parse tree.
private void	match(LexicalUnit expected)	Matches the current token against the expected token type.
private ParseTree	parseAssign()	Parse assignment statement.
private ParseTree	parseCode()	Parse code block.
private ParseTree	parseCond()	Parse condition.
private ParseTree	parseCondAtom()	Parse condition atom.
private ParseTree	parseCondComp()	Parse condition comparison.
private ParseTree	parseCondImpl()	Parse condition with implication.
private ParseTree	parseExprAddSub()	Parse addition and subtraction.
private ParseTree	parseExprArith()	Parse arithmetic expression.
private ParseTree	parseExprMulDiv()	Parse multiplication and division.
private ParseTree	parseExprPrimary()	Parse primary expression.
private ParseTree	parseExprUnary()	Parse unary expression.
private ParseTree	parseIf()	Parse If statement.
private ParseTree	parseInput()	Parse Input statement.
private ParseTree	parseInstruction()	Parse instruction statement.
private void	parseOptionalElse(ParseTree node)	Handles the optional Else branch in an If statement.
private ParseTree	parseOutput()	Parse Output statement.
ParseTree	parseProgram()	Parse the entire program.
private ParseTree	parseWhile()	Parse While statement.

Methods inherited from class java.lang.Object

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

Field Details

lexer

private final LexicalAnalyzer lexer

The lexical analyzer providing tokens for parsing.

currentToken

private Symbol currentToken

The current token being analyzed

Constructor Details

Parser

public Parser(LexicalAnalyzer lexer)
       throws IOException

Creates a parser with the given lexical analyzer.

Parameters:

lexer - the lexical analyzer

Throws:

Exception - if an error occurs during token retrieval

IOException

Method Details

match

private void match(LexicalUnit expected)
            throws ParseException,
IOException

Matches the current token against the expected token type. Advances to the next token if matched; throws an error otherwise.

Parameters:

expected - the expected token type

Throws:

ParseException - if the current token does not match the expected type

IOException - if an I/O error occurs during token retrieval

dummy

private Symbol dummy(NonTerminal nt)

Creates a dummy symbol for non-terminal nodes in the parse tree.

Parameters:

nt - the non-terminal symbol

Returns:

a Symbol representing the non-terminal

parseProgram

public ParseTree parseProgram()
                       throws ParseException,
IOException

Parse the entire program.

Returns:

the parse tree node for Program

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseCode

private ParseTree parseCode()
                     throws ParseException,
IOException

Parse code block.

Returns:

the parse tree node for Code

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseInstruction

private ParseTree parseInstruction()
                            throws ParseException,
IOException

Parse instruction statement.

Returns:

the parse tree node for Instruction

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseAssign

private ParseTree parseAssign()
                       throws ParseException,
IOException

Parse assignment statement.

Returns:

the parse tree node for Assign

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseIf

private ParseTree parseIf()
                   throws ParseException,
IOException

Parse If statement.

Returns:

the parse tree node for If

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseOptionalElse

private void parseOptionalElse(ParseTree node)
                        throws ParseException,
IOException

Handles the optional Else branch in an If statement. If the current token is ELSE, it parses the else branch.

Parameters:

node - the If parse tree node to which the else branch will be added

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseWhile

private ParseTree parseWhile()
                      throws ParseException,
IOException

Parse While statement.

Returns:

the parse tree node for While

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseOutput

private ParseTree parseOutput()
                       throws ParseException,
IOException

Parse Output statement.

Returns:

the parse tree node for Output

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseInput

private ParseTree parseInput()
                      throws ParseException,
IOException

Parse Input statement.

Returns:

the parse tree node for Input

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseCond

private ParseTree parseCond()
                     throws ParseException,
IOException

Parse condition.

Returns:

the parse tree node for Cond

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseCondImpl

private ParseTree parseCondImpl()
                         throws ParseException,
IOException

Parse condition with implication.

Returns:

the parse tree node for CondImpl

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseCondComp

private ParseTree parseCondComp()
                         throws ParseException,
IOException

Parse condition comparison.

Returns:

the parse tree node for CondComp

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseCondAtom

private ParseTree parseCondAtom()
                         throws ParseException,
IOException

Parse condition atom.

Returns:

the parse tree node for CondAtom

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseExprArith

private ParseTree parseExprArith()
                          throws ParseException,
IOException

Parse arithmetic expression.

Returns:

the parse tree node for ExprArith

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseExprAddSub

private ParseTree parseExprAddSub()
                           throws ParseException,
IOException

Parse addition and subtraction.

Returns:

the parse tree node for ExprAddSub

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseExprMulDiv

private ParseTree parseExprMulDiv()
                           throws ParseException,
IOException

Parse multiplication and division.

Returns:

the parse tree node for ExprMulDiv

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseExprUnary

private ParseTree parseExprUnary()
                          throws ParseException,
IOException

Parse unary expression.

Returns:

the parse tree node for ExprUnary

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs

parseExprPrimary

private ParseTree parseExprPrimary()
                            throws ParseException,
IOException

Parse primary expression.

Returns:

the parse tree node for ExprPrimary

Throws:

ParseException - if a syntax error occurs

IOException - if an I/O error occurs