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citizen428/ycombinator-step1.clj

Created December 14, 2010 20:42
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ycombinator-step1.clj
(ns step1)
(defn fact
[n]
(if (< n 2) 1 (* n (fact (dec n)))))
;; (fact 5) => 120
Raw
ycombinator-step2.clj
(ns step2)
(defn fact
[f]
(fn [n]
(if (< n 2) 1 (* n ((f f) (dec n))))))
;; ((fact fact) 5) => 120
Raw
ycombinator-step3.clj
(ns step3)
(defn yrecur
[f]
(f f))
(def fact
(yrecur (fn [f]
(fn [n]
(if (< n 2) 1 (* n ((f f) (dec n))))))))
;; (fact 5) => 120
Raw
ycombinator-step4.clj
(ns step4)
(defn yrecur
[f]
(f f))
(def fact
(yrecur
(fn [f]
(let [g (fn [n] ((f f) n))]
(fn [n]
(if (< n 2) 1 (* n (g (dec n)))))))))
;; (fact 5) => 120
Raw
ycombinator-step5.clj
(ns step5)
(defn yrecur
[f]
(f f))
(defn wrap
[h]
(yrecur
(fn [f]
(let [g (fn [n] ((f f) n))]
(h g)))))
(def fact
(wrap
(fn [g]
(fn [n]
(if (< n 2) 1 (* n (g (dec n))))))))
;; (fact 5) => 120
Raw
ycombinator-step6.clj
(ns step6)
(defn yrecur
[f]
(f f))
(defn wrap
[h]
(yrecur
(fn [f]
(h (fn [n] ((f f) n))))))
(def fact
(wrap
(fn [g]
(fn [n]
(if (< n 2) 1 (* n (g (dec n))))))))
;; (fact 5) => 120
Raw
ycombinator-step7.clj
(ns step7)
(defn Y
[h]
((fn [f] (f f)) (fn [f]
(h (fn [n]
((f f) n))))))
(def fact
(Y (fn [g]
(fn [n]
(if (< n 2) 1 (* n (g (dec n))))))))
;; (fact 5) => 120
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