1. Reverse
Polish
Notation

2. BEDMAS
BIDMAS
BODMAS
PEMDAS

3. 6,2/1,2+*
*
/ +
6 2 1 2
/ 6,2,1,2,+*/
*
+
6 2 1 2

4. 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. Reverse Polish Notation Examples
7,4+3- 7+4-3
1,2*3+ 1*2+3
1,2+3* (1+2) *3
5,9,2*+ 5+9*2
1,2*3,4*+ 1*2+3*4

6. 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