solution to 2.19

diff --git a/src/sicp/ex2_19.clj b/src/sicp/ex2_19.clj
new file mode 100644 (file)
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+++ b/src/sicp/ex2_19.clj
@@ -0,0 +1,28 @@
+(ns sicp.ex2_19
+  (:use [sicp utils]
+       [clojure test]))
+
+(declare no-more? first-denomination except-first-denomination)
+
+(defn cc [amount coin-values]
+  (cond (= amount 0) 1
+       (or (< amount 0) (no-more? coin-values)) 0
+       :else
+       (+ (cc amount
+              (except-first-denomination coin-values))
+          (cc (- amount
+                 (first-denomination coin-values))
+              coin-values))))
+
+(defn no-more? [lst] (empty? lst))
+(defn first-denomination [lst] (first lst))
+(defn except-first-denomination [lst] (rest lst))
+
+;; tests
+(def *us-coins* (list 50 25 10 5 1))
+(def *uk-coins* (list 100 50 20 10 5 2 1 0.5))
+
+(deftest test-us-coins-change-for-100-cents
+  (are [x y] [= x y]
+       (cc 100 *us-coins*) 292
+       (cc 100 *uk-coins*) 104561))
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