; defining variables
(define name "Marty")
(define age (- 31 2))
(define b (< 3 7))

; (square x) computes x * x, or x squared.
; Works for integers, real numbers, or any numeric type.
(define (square x) (* x x))

; (factorial n) computes n!, or 1 * 2 * 3 * ... * (n-1) * n.
; assumes n is non-negative.
(define (factorial n)
    (if (= n 0) 1
        (* n (factorial (- n 1)))))