From: Ramakrishnan Muthukrishnan Date: Mon, 2 Aug 2010 18:41:26 +0000 (+0530) Subject: examples till ex 2.33. X-Git-Url: https://git.rkrishnan.org/%3C?a=commitdiff_plain;h=be124270e19b9a4cc0e554cc4ebebdf71edb8fd8;p=sicp.git examples till ex 2.33. --- diff --git a/src/sicp/ch2_2.clj b/src/sicp/ch2_2.clj index 21d9f33..30fd55b 100644 --- a/src/sicp/ch2_2.clj +++ b/src/sicp/ch2_2.clj @@ -1,6 +1,7 @@ (ns sicp.ch2-2 (:refer-clojure :exclude (map)) - (:use (sicp [ch1-2 :only (fib)]))) + (:use [sicp [ch1-2 :only (fib)]] + [clojure.test])) (cons 1 (cons 2 @@ -155,4 +156,53 @@ ([low high] (if (> low high) nil - (cons low (enumerate-interval (+ low 1) high))))) \ No newline at end of file + (cons low (enumerate-interval (+ low 1) high))))) + +;; same as flatten/fringe +(defn enumerate-tree [tree] + (cond (nil? tree) nil + (not (seq? tree)) (list tree) + :else (concat (enumerate-tree (first tree)) + (enumerate-tree (next tree))))) + +(defn square [x] (* x x)) + +;; define sum of odd squares in terms of myfilter-2, enumerate, accumulate +(defn sum-of-odd-squares [tree] + (->> tree + (enumerate-tree) + (filter odd?) + (map square) + (accumulate + 0))) + +(deftest test-sum-of-odd-squares + (is [= (sum-of-odd-squares '((1) (2) (3 4) ((5) (((6) (7)) (8))))) + (reduce + (map #(* % %) (filter odd? (range 1 9))))])) + +(defn even-fibs-new [n] + (->> n + (enumerate-interval ,,,) + (map fib ,,,) + (filter even? ,,,) + (accumulate cons nil ,,,))) + +(defn list-fib-squares [n] + (->> n + (enumerate-interval ,,,) + (map fib ,,,) + (map square ,,,) + (accumulate cons nil ,,,))) + +(defn product-of-squares-of-odd-elements [sequence] + (accumulate * + 1 + (map square + (filter odd? sequence)))) + +;; note how beautiful and clear the clojure ->> macro is! +(defn product-of-squares-of-odd-elements [sequence] + (->> sequence + (filter odd? ,,,) + (map square ,,,) + (accumulate * 1 ,,,))) +