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-rw-r--r--one/fourteen.scm29
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+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+;;; source from section 1.2.2
+
+(define-module (one fourteen)
+ #:export (count-change
+ cc
+ first-denomination))
+
+(define (count-change amount)
+ (cc amount 5))
+
+(define (cc amount kinds-of-coins)
+ (cond ((= amount 0) 1)
+ ((or (< amount 0) (= kinds-of-coins 0)) 0)
+ (else (+ (cc amount
+ (- kinds-of-coins 1))
+ (cc (- amount
+ (first-denomination kinds-of-coins))
+ kinds-of-coins)))))
+
+(define (first-denomination kinds-of-coins)
+ (cond ((= kinds-of-coins 1) 1)
+ ((= kinds-of-coins 2) 5)
+ ((= kinds-of-coins 3) 10)
+ ((= kinds-of-coins 4) 25)
+ ((= kinds-of-coins 5) 50)))