From: Ramakrishnan Muthukrishnan Date: Sun, 12 Sep 2010 06:15:09 +0000 (+0530) Subject: adding the "sets as trees" section code X-Git-Url: https://git.rkrishnan.org/components/com_hotproperty/frontends/%22file:/htmlfontify-example.html?a=commitdiff_plain;h=86a3fa6a261dd101bc7e7f3bfdf8f8467cc432ea;p=sicp.git adding the "sets as trees" section code --- diff --git a/src/sicp/ch2_3.clj b/src/sicp/ch2_3.clj index 548d3aa..a69973c 100644 --- a/src/sicp/ch2_3.clj +++ b/src/sicp/ch2_3.clj @@ -104,3 +104,35 @@ (rest set2))) (< x1 x2) (intersection-set (rest set1) set2) (< x2 x1) (intersection-set (rest set2) set1))))) + +;;; sets as trees +;;; trees using lists +;;; every node is a list of 3 elements: entry, left tree and right tree +(defn entry [tree] + (first tree)) + +(defn left-branch [tree] + (second tree)) + +(defn right-branch [tree] + (second (rest tree))) + +(defn make-tree [entry left right] + (list entry left right)) + +(defn element-of-set? [x set] + (cond (empty? set) false + (= (entry set) x) true + (< x (entry set)) (element-of-set? x (left-branch set)) + (> x (entry set)) (element-of-set? x (right-branch set)))) + +(defn adjoin-set [x set] + (cond (empty? set) (make-tree x '() '()) + (= x (entry set)) set + (< x (entry set)) (make-tree (entry set) + (adjoin-set x (left-branch set)) + (right-branch set)) + (> x (entry set)) (make-tree (entry set) + (left-branch set) + (adjoin-set x (right-branch set))))) +