Examples of function definitions

1. Write a function that will add 3 to a single number.

(defun plus3 (n)

(+ 3 n))

2. Write a function that will add 3 to each of a list of numbers

(defun listplus3 (list)

(cond

((null list) nil) ; is the list empty

( (numberp list) (+ 3 list)) ; does the list have a single number?

( t (cons (listplus3 (car list)) (listplus3 (cdr list))))

)

)