Oban numbers

oban.clj

; from http://programmingpraxis.com/2010/10/01/oban-numbers/

(ns oban)

(def base [nil nil "three" nil "five" "six" "seven" "eight" "nine"])

(def dec ["twenty" "thirty" "fifty" nil "sixty" "seventy" "eigthy" "ninety"])

(def teens  ["ten" "eleven" "twelve" "thirteen" "fourteen" "fifteen" "sixteen" "seventeen" "eighteen" "nineteen"])

(declare combine comb)

(defn gen-seq []
  (let [nums (concat base teens (combine dec base))]
    (concat nums (combine base ["hundred"] nums))))

(defn combine [& colls]
  (reduce comb colls))

(defn comb [head tail]
 (for [h head t tail]
    (if (or (nil? t) (nil? h))
      nil
      (str h " " t))))

(time 
  (doall
    (for [word (gen-seq) :when word]
      (print word "\n"))))