solution to 2.61

diff --git a/src/sicp/ex2_61.clj b/src/sicp/ex2_61.clj
new file mode 100644 (file)
index 0000000..c897c61
--- /dev/null
+++ b/src/sicp/ex2_61.clj
@@ -0,0 +1,19 @@
+(ns sicp.ex2_61
+  (:use [sicp.ex2_54 :only (equal? eq?)]
+        [clojure.test]))
+
+(defn adjoin-set [x set]
+  (let [x1 (first set)]
+    (cond (empty? set) (cons x set)
+          (= x x1) set
+          (< x x1) (cons x set)          
+          (> x x1) (cons x1 (adjoin-set x (rest set))))))
+
+(deftest test-adjoin
+  (are [x y] [= x y]
+       (adjoin-set 0 '())    '(0)
+       (adjoin-set 1 '(2 3)) '(1 2 3)
+       (adjoin-set 3 '(1 2 3)) '(1 2 3)
+       (adjoin-set 3 '(1 2 4)) '(1 2 3 4)
+       (adjoin-set 4 '(1 2 4)) '(1 2 4)
+       (adjoin-set 4 '(1 2 3)) '(1 2 3 4)))
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