operate on the top two stack items:
2 2 .s + .s . 2 1 - . 7 3 mod .
The operands of
mod are in the same order
as in the corresponding infix expression (this is generally the case in
Parentheses are superfluous (and not available), because the order of the words unambiguously determines the order of evaluation and the operands:
3 4 + 5 * . 3 4 5 * + .
Assignment: What are the infix expressions corresponding to the Forth code above? Write
6-7*8+9in Forth notation1.
To change the sign, use
2 negate .
Assignment: Convert -(-3)*4-5 to Forth.
/mod performs both
7 3 /mod . .
 This notation is also known as Postfix or RPN (Reverse Polish Notation).