solution to 2.30

diff --git a/src/sicp/ex2_30.clj b/src/sicp/ex2_30.clj
new file mode 100644 (file)
index 0000000..e79f06b
--- /dev/null
+++ b/src/sicp/ex2_30.clj
@@ -0,0 +1,25 @@
+(ns sicp.ex2_30
+  (:use [clojure.test]))
+
+;; without map
+(defn square-tree [tree]
+  (cond (nil? tree) nil
+       (not (seq? tree)) (* tree tree)
+       :else (cons (square-tree (first tree))
+                   (square-tree (next tree)))))
+
+(deftest test-sq-tree
+  (are [x y] [= x y]
+       (square-tree '(1 (2 (3 4) 5) (6 7))) '(1 (4 (9 16) 25) (36 49))))
+
+;; with map
+(defn square-tree-with-map [tree]
+  (map (fn [sub-tree]
+        (if (seq? sub-tree)
+          (square-tree-with-map sub-tree)
+          (* sub-tree sub-tree)))
+       tree))
+
+(deftest test-sq-tree-map
+  (are [x y] [= x y]
+       (square-tree-with-map '(1 (2 (3 4) 5) (6 7))) '(1 (4 (9 16) 25) (36 49))))