Postfix Notation

• Postfix notation is the useful form of intermediate code if the given language is expressions.
• Postfix notation is also called as 'suffix notation' and 'reverse polish'.
• Postfix notation is a linear representation of a syntax tree.
• In the postfix notation, any expression can be written unambiguously without parentheses.
• The ordinary (infix) way of writing the sum of x and y is with operator in the middle: x * y. But in the postfix notation, we place the operator at the right end as xy *.
• In postfix notation, the operator follows the operand.

Example

Production

1. E  →  E1 op E2                       
2. E  →  (E1)  
3. E   →  id  

Semantic Rule	Program fragment
E.code = E1.code || E2.code || op	print op
E.code = E1.code
E.code = id	print id