Tautalogy evaluator help
What I'm trying to do is I have an expression that entered like
(P --> Q) <--> (P v ~Q) as a regular string. Then the string is parsed to see if the expression is a tautology. I have two case structures to process the operands and their priorities. And public void evaluate() does the parsing and uses a stack.
But right I'm completely lost as to figuring out the best way to do this. Can somebody give me any ideas, or point me in the right direction?
Here what I have so far for code:
import java.util.Stack;
publicclass TautologyExpress{
public String express;
public TautologyExpress(String string)
{
express="("+string+")";
}
publicvoid evaluate()
{
Stack stack =new Stack();
int a = express.length();
int i;
for(i = 0; i< a; i++)
{
if(express.charAt(i)=='P')
{
stack.push(express.charAt(i));
}
if(express.charAt(i)=='Q')
{
stack.push(express.charAt(i));
}
if(express.charAt(i)=='~')
{
if(!stack.isEmpty())
{
while(Priority((Character)stack.peek()) >= Priority(express.charAt(i)))
express += stack.pop();
}
}
}
}
publicboolean check(char ch)
{
switch(ch)
{
case'P':
returntrue;
case'Q':
returntrue;
}
returnfalse;
}
publicboolean Operator(char ch)
{
switch(ch)
{
case'|':// represents <>
case'>':
case'^':
case'v':
case'~':
case'(':
case')':
case'#':
returntrue;
default:
returnfalse;
}
}
publicint Priority(char ch)
{
switch(ch)
{
case')':
case'#':
return 0;
case'|':
return 1;
case'>':
return 2;
case'v':
return 3;
case'^':
return 4;
case'~':
return 5;
case'(':
return 6;
}
return -1;
}
publicstaticvoid main(String []args)
{
TautologyExpress obj=new TautologyExpress("(P > Q) | (~ P v Q)");
obj.evaluate();
}
}
