From fc933303d5b5c15e3f912f74dc1af6c1ba3118c5 Mon Sep 17 00:00:00 2001
From: rsiddharth <s@ricketyspace.net>
Date: Thu, 22 Nov 2018 22:54:49 -0500
Subject: Add (net ricketyspace sicp two nineteen).

---
 net/ricketyspace/sicp/two/nineteen.scm | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 net/ricketyspace/sicp/two/nineteen.scm

(limited to 'net/ricketyspace')

diff --git a/net/ricketyspace/sicp/two/nineteen.scm b/net/ricketyspace/sicp/two/nineteen.scm
new file mode 100644
index 0000000..e4f7259
--- /dev/null
+++ b/net/ricketyspace/sicp/two/nineteen.scm
@@ -0,0 +1,26 @@
+;;;; License: CC0-1.0
+
+(define-module (net ricketyspace sicp two nineteen)
+  #:export (us-coins uk-coins cc))
+
+(define us-coins (list 50 25 10 5 1))
+(define uk-coins (list 100 50 20 10 5 2 1 0.5))
+
+(define (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)))))
+
+(define (no-more? coin-values)
+  (null? coin-values))
+
+(define (except-first-denomination coin-values)
+  (cdr coin-values))
+
+(define (first-denomination coin-values)
+  (car coin-values))
-- 
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