as you can seeit' not trivial to convert infix expressions to postfix expressions is all this trouble really necessaryyesthe payoff comes when you evaluate postfix expression before we show how simple the algorithm islet' examine how human might carry out such an evaluation how humans evaluate postfix figure shows how human can evaluate postfix expression using visual inspection and pencil start with the first operator on the leftand draw circle around it and the two operands to its immediate left then apply the operator to these two operands--performing the actual arithmetic--and write down the result inside the circle in the figureevaluating + gives figure visual approach to postfix evaluation of +* +/now go to the next operator to the rightand draw circle around itthe circle you already drewand the operand to the left of that apply the operator to the previous circle and the new operandand write the result in the new circle here * gives continue this process until all the operators have been applied + is and / is the answer is the result in the largest circle - is rules for postfix evaluation how do we write program to reproduce this evaluation processas you can seeeach time you come to an operatoryou apply it to the last two operands you've seen this suggests that it might be appropriate to store the operands on stack (this is the opposite of the infix to postfix translation algorithmwhere operators were stored on the stack you can use the rules shown in table to evaluate postfix expressions table evaluating postfix expression item read from postfix expression action operand push it onto the stack operator pop the top two operands from the stackand apply the operator to them push the result