From: Ramakrishnan Muthukrishnan Date: Sat, 10 Jul 2010 06:55:33 +0000 (+0530) Subject: another implementation of reverse X-Git-Url: https://git.rkrishnan.org/pf/content/en/footer/index.html?a=commitdiff_plain;h=008a2bb7976b75e2b25d85e20aa032b5ad2d2d1a;p=sicp.git another implementation of reverse --- diff --git a/src/sicp/ex2_18.clj b/src/sicp/ex2_18.clj index b56c4e8..b74f723 100644 --- a/src/sicp/ex2_18.clj +++ b/src/sicp/ex2_18.clj @@ -1,11 +1,12 @@ (ns sicp.ex2_18 - (:use [clojure test])) + (:use [clojure test]) + (:refer-clojure :exclude (reverse))) -(defn turn-around-1 [lst] +(defn reverse-1 [lst] (reduce #(cons %2 %1) '() lst)) -(defn turn-around-2 [lst] +(defn reverse-2 [lst] (let [reverse (fn [lst1 lst2] (if (empty? lst1) lst2 @@ -13,12 +14,19 @@ (reverse lst '()))) -(deftest test-turn-around-1 +(defn reverse-3 [lst] + (if (empty? lst) + nil + (cons (last lst) (reverse-3 (butlast lst))))) + +(deftest test-reverse-1 (are [x y] [= x y] - (turn-around-1 (list 1 2 3 4)) (list 4 3 2 1) - (turn-around-1 (list 1 4 9 16 25)) (list 25 16 9 4 1))) + (reverse-1 (list 1 2 3 4)) (list 4 3 2 1) + (reverse-1 (list 1 4 9 16 25)) (list 25 16 9 4 1) + (reverse-1 (list (list 1 2) (list 3 4))) (list (list 3 4) (list 1 2)))) -(deftest test-turn-around-2 +(deftest test-reverse-2 (are [x y] [= x y] - (turn-around-2 (list 1 2 3 4)) (list 4 3 2 1) - (turn-around-2 (list 1 4 9 16 25)) (list 25 16 9 4 1))) + (reverse-2 (list 1 2 3 4)) (list 4 3 2 1) + (reverse-2 (list 1 4 9 16 25)) (list 25 16 9 4 1) + (reverse-1 (list (list 1 2) (list 3 4))) (list (list 3 4) (list 1 2))))