3. Evaluating RPN• Uses a stack and two simple rules. Reading left to right …….• 1. If a value appears next in the expression, push this value on to the stack.• 2. If an operator appears next, pop two items from the top of the stack and push the result of the operation on to the stack.
5. Converting from infix to postfix ‘Shunting yard algorithm’• Read each character • Calculator - another• If its an operand, add it to the output• If it’s an operator then – If there’s a higher BODMAS priority operator at the top of the stack, pop it – Push it on the stack• At the end, pop everything off the operator stack