flat

[procedure] flat x (o stringstoo)

(def flat (x (o stringstoo))
  ((rfn f (x acc)
     (if (or (no x) (and stringstoo (is x "")))
          acc
         (and (atom x) (no (and stringstoo (isa x 'string))))
          (cons x acc)
         (f (car x) (f (cdr x) acc))))
   x nil))