algorithm to evaluate a Postfix expression

Dear Friends

Here is the algorithm to evaluate a Postfix expression

1. Add a right parenthesis “)” at the end of P. [This acts as a sentinel.]

2. Scan P from left to right and repeat Steps 3 and 4 for each element of P until the sentinel “)” is encountered.

3. If an operand is encountered, put it on STACK.

4. If an operator x is encountered, then:
a. Remove the two top elements of STACK, where A is the top element and B is the next-top element.
b. Evaluate B⊗A.
c. Place the result of (b) back on STACK.
[End of If structure.]

[End of Step 2 loop.]

5. Set VALUE equal to the top element to STACK

6. Exit