(defn doub [f]
(fn [x] (f (f x))))
+(deftest test-doub-doub-doub-inc-5
+ (is (= (((doub (doub doub)) inc) 5)
+ 21)))
+
+(deftest test-doub-inc-1
+ (is (= ((doub inc) 1)
+ 3)))
+
+(deftest test-doub-doub-inc-1
+ (is (= (((doub (doub doub)) inc) 1)
+ 17)))
+
(comment
(((doub (doub doub)) inc) 5)
;;=> 21