(mac if args
  ; with arguments a,         return a
  ; with arguments a b,       return b if a is true, otherwise nil
  ; with arguments a b c,     return b if a is true, otherwise return c
  ; with arguments a b c d,   return b if a is true, otherwise return d if c is true, otherwise nil
  ; with arguments a b c d e, return b if a is true, otherwise return d if c is true, otherwise e
  ; and so on for subsequent arguments
  (cond (no args) nil
        (cond (cdr args)
              (cond (cddr args)
                    `(cond ,(car args) ,(cadr args) (if ,@(cddr args)))
                    `(cond ,(car args) ,(cadr args)))
              (car args))))

(def map (f things)
  ; transforms the list 'things by applying 'f to each item
  ; returns the resulting list
  (if (no things)
      nil
      (pair? things)
      (cons (f (car things)) (map f (cdr things)))
      (map f (list things))))