1   #! /usr/bin/env racket
  2   
  3   #lang racket/base
  4   
  5   (define (add1 . nums) ; Take any number of arguments, including zero.
  6     (define (op numl)
  7       (cond
  8         [(eq? '() numl) (void)]
  9         [else
 10           (displayln (+ 1 (car numl)))
 11           (op (cdr numl))]))
 12     (op nums)) 
 13   
 14   (add1 1 3 7)
 15   (add1)