From 736da82a653cb517ce38c4e7d0d2e93c19a9f7b5 Mon Sep 17 00:00:00 2001 From: Ramakrishnan Muthukrishnan <vu3rdd@gmail.com> Date: Mon, 14 Jun 2010 15:08:27 +0530 Subject: [PATCH] solution to 2.15 --- src/sicp/ch2_1_extended.clj | 2 +- src/sicp/ex2_15.clj | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+), 1 deletion(-) create mode 100644 src/sicp/ex2_15.clj diff --git a/src/sicp/ch2_1_extended.clj b/src/sicp/ch2_1_extended.clj index dca737b..0631e7d 100644 --- a/src/sicp/ch2_1_extended.clj +++ b/src/sicp/ch2_1_extended.clj @@ -42,4 +42,4 @@ (let [one (make-interval 1 1)] (div-interval one (add-interval (div-interval one r1) - (div-interval one r2))))) \ No newline at end of file + (div-interval one r2))))) diff --git a/src/sicp/ex2_15.clj b/src/sicp/ex2_15.clj new file mode 100644 index 0000000..7072794 --- /dev/null +++ b/src/sicp/ex2_15.clj @@ -0,0 +1,32 @@ +(ns sicp.ex2_15 + (:use [sicp utils ch2_1_extended ex2_7 ex2_8 ex2_12] + [clojure.test])) + +(def r1 (make-center-percent 1000 0.01)) +(def r2 (make-center-percent 100 0.01)) + +(def r3 (sub-interval (add-interval r1 r2) r2)) +;;=> (999.8799999999999 1000.1200000000001) + +(percentage r3) +;;=> 0.012000000000011824 + +(center r3) +;;=> 1000.0 + +(comment +"This shows that even if you add and subtract an interval (r2) from +another interval, we get back an interval which is not the same as +the original one r1. Let us look at the range as (center, percentage) +pair. + r1 = c1 +/- w1 + r2 = c2 +/- w2 + +Now r1+r2-r2 = c1 + c2 - c1 +/- (2*w1+w2) + = c1 +/- (2*w1 + w2) + +i.e. we have a new percentage width as the errors add up. The inference +from this is that, we reduce the number of ranges in a calculation to +get a more accurate range. So, yes, Eva Lu Ator is right. +" + ) \ No newline at end of file -- 2.45.2