RosettaCodeData/Task/Church-numerals/Clojure/church-numerals.clj

19 lines
538 B
Clojure

(defn zero [f] identity)
(defn succ [n] (fn [f] (fn [x] (f ((n f) x)))))
(defn add [n,m] (fn [f] (fn [x] ((m f)((n f) x)))))
(defn mult [n,m] (fn [f] (fn [x] ((m (n f)) x))))
(defn power [b,e] (e b))
(defn to-int [c] ((c inc) 0))
(defn from-int [n]
(letfn [(countdown [i] (if (zero? i) zero (succ (countdown (- i 1)))))]
(countdown n)))
(def three (succ (succ (succ zero))))
(def four (from-int 4))
(doseq [n [(add three four) (mult three four)
(power three four) (power four three)]]
(println (to-int n)))