Class SLR

java.lang.Object
  SLR

public class SLR

extends java.lang.Object

This class implements the SLR(0) method for syntax analysis. Usage:
java SLR "input" grammar.
For instance,
java SLR "(1+2)*3" ../Data/ETF.txt produces the successive stack contents during the analysis of the expression (1+2)*3 using the ETF grammar. If the grammar is not SLR, an error message "Grammar not SLR: S/R conflict" or "Grammar not SLR: S/R conflict" is issued. If the expression is not correct, an error message "syntax error" or "end of input reached" is issued.

Field Summary

Alphabet	alphabet The input alphabet;
char[]	expression The expression to analyze.
Grammar	G The current context-free grammar.
int[][]	LRReduceTable
int[][]	LRShiftTable The shift table.
int	position The current index.
java.util.Stack	stack The stack used to store the LR states.

Method Summary

void	advance() Advance one character to the right on input.
short	current() Returns the current token of the input.
InfoNFA	LRAutomaton() Computes the LR(0) automaton.
int[][]	LRReduceTable(InfoDFA a)
int[][]	LRShiftTable(InfoDFA a) Computes the SLR(0) shift table.
static void	main(java.lang.String[] args)
void	push(short c) Push the character c on the stack.

Methods inherited from class java.lang.Object

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

Field Detail

expression

public char[] expression

The expression to analyze.

position

public int position

The current index.

stack

public java.util.Stack stack

The stack used to store the LR states.

G

public Grammar G

The current context-free grammar.

alphabet

public Alphabet alphabet

The input alphabet;

LRShiftTable

public int[][] LRShiftTable

The shift table.

LRReduceTable

public int[][] LRReduceTable

Method Detail

advance

public void advance()

Advance one character to the right on input.

current

public short current()

Returns the current token of the input. Discards possible space characters.

push

public void push(short c)

Push the character c on the stack. Actually push the state reached in the LR automaton from the state p at top of the stack under input c.

Parameters:

c - the input character

Returns:

the state next(p,c)

LRAutomaton

public InfoNFA LRAutomaton()

Computes the LR(0) automaton.

LRShiftTable

public int[][] LRShiftTable(InfoDFA a)

Computes the SLR(0) shift table. The positive values correspond to the shift part, the negative ones to the reduce part.

LRReduceTable

public int[][] LRReduceTable(InfoDFA a)
                      throws java.lang.Exception

Throws:

java.lang.Exception

main

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

Throws:

java.io.IOException