How to use the mod function on LISPS using control structures

Question

I am new to LISP, is there a way of using mod with control structures, if statements.

for instance having (if (mod 4 2) (+ 2 2) (- 9 2)). What does the expression return, 0, nil, T?

Answer 1

In Lisp, the only false value is nil, so 0 is true. Thus (mod 4 2) returns 0 which is true which means that

(if (mod 4 2)
    (+ 2 2)
    (- 9 2))

returns 4, while

(if (/= 0 (mod 4 2))
    (+ 2 2)
    (- 9 2))

returns 7.