From: Ramakrishnan Muthukrishnan Date: Tue, 4 May 2010 10:56:04 +0000 (+0530) Subject: cleaner implementation making use of sum X-Git-Url: https://git.rkrishnan.org/pf/content/%22news.html/frontends/webapi.txt?a=commitdiff_plain;h=a574e2a7e1bf084315054a1e7e4cdb48d60dcb05;p=sicp.git cleaner implementation making use of sum --- diff --git a/src/sicp/ex1_29.clj b/src/sicp/ex1_29.clj index cf30a23..0f36ae5 100644 --- a/src/sicp/ex1_29.clj +++ b/src/sicp/ex1_29.clj @@ -3,20 +3,23 @@ [clojure.contrib trace test-is])) ;; simpson's rule of integration -(defn make-fac [k n] - (cond (= k 0) 1 - (= k n) 1 - (even? k) 2 - :else 4)) - -(defn simpson-sum [term a next-fn b n k] - (let [fac (make-fac k n)] - (if (> k n) - 0 - (+ (* fac (term a)) - (simpson-sum term (next-fn a) next-fn b n (+ k 1)))))) +(defn sum [term a next b] + (if (> a b) + 0 + (+ (term a) + (sum term (next a) next b)))) (defn simpson-rule [f a b n] - (let [h (/ (- b a) n)] - (* (simpson-sum f a #(+ h %) b n 0) - (/ h 3.0)))) + (let [h (/ (- b a) n) + make-fac (fn [k] + (cond (= k 0) 1 + (= k n) 1 + (even? k) 2 + :else 4)) + simp-term (fn [k] + (* (make-fac k) + (f (+ a (* k h)))))] + (* (/ h 3.0) + (sum simp-term 0 inc n)))) + +;;; lots of great ideas in the above exercise. \ No newline at end of file