Add q78

src/ex/q078.clj

@@ -0,0 +1,9 @@
+;; https://4clojure.oxal.org/#/problem/078
+
+(ns ex.q078)
+
+(defn ans
+  "Problem 78, Reimplement Trampoline"
+  [f & xs]
+  (loop [fn-or-val (apply f xs)]
+    (if (fn? fn-or-val) (recur (fn-or-val)) fn-or-val)))

test/ex/q078_test.clj

@@ -0,0 +1,17 @@
+;; https://4clojure.oxal.org/#/problem/078
+
+(ns ex.q078-test
+  (:require [clojure.test :as t]
+            [ex.q078 :as sut]))
+
+(t/deftest test-q78
+  (t/testing "Problem 78, Reimplement Trampoline"
+    (t/is (= 82
+             (letfn [(triple [x] #(sub-two (* 3 x)))
+                     (sub-two [x] #(stop? (- x 2)))
+                     (stop? [x] (if (> x 50) x #(triple x)))]
+               (sut/ans triple 2))))
+    (t/is (= [true false true false true false]
+             (letfn [(my-even? [x] (if (zero? x) true #(my-odd? (dec x))))
+                     (my-odd? [x] (if (zero? x) false #(my-even? (dec x))))]
+               (map (partial sut/ans my-even?) (range 6)))))))