;;; English number words
;;; Returns nil if n < 0.

(defun full-words (n)
  (cond
   ((< n 0) nil)
   ((< n 10) (digit-word n))
   (t (concatenate 'string
		   (full-words (floor n 10))
		   "-"
		   (digit-word (mod n 10))
		   )
      )
   )
  )

(defun digit-word (n)
  (elt '("zero" "one" "two" "three" "four" "five" "six" "seven"
	 "eight" "nine") n)
  )