1. Infix to Postfix Conversion
CS212 & CS240
DJ Foreman

2. The algorithms convert infix notation to postfix
use a stack of operators and operands
NOTE: you can either place the data in the stack as you read it OR put it all in a temporary queue, then pull from that queue
evaluate a postfix expression
uses stack from step 1
evaluate an infix expression
use (1) and (2) together

3. Infix to Postfix (algorithm 1)
while (more input) // ended by a $
if '(' push it on stack with priority (precedence) 0
if operand - send to output (enqueue – separate from temp queue)
if ')'
output operators till '('.
Unstack & discard the '('.
Discard the ')'
if operator
while precedence (operator) < precedence (top)
unstack and output operators
unstack and enqueue any operators remaining on stack
Result will be a queue in postfix order
Precedence (high to low): ^ * / + - (

4. Evaluating Postfix (algorithm 2)
while (more input)
if (operand) push on stack
if (operator) apply to top 2 stack items and replace them (on the stack) with the result of the operation
E.g.; given the queue form algorithm 1 has: now has 23+ (where the 2 is in the front), the stack will contain the 2 at the bottom, the 3 above it and seeing the +, you pull the 3 and 2, do the addition, putting the 5 back on top
When no input remains, remaining item on the operand stack is value of the expression