Initial data commit

Task/Digital-root-Multiplicative-digital-root/Racket/digital-root-multiplicative-digital-root.rkt

@@ -0,0 +1,23 @@
+#lang racket
+(define (digital-product n)
+  (define (inr-d-p m rv)
+    (cond
+      [(zero? m) rv]
+      [else (define-values (q r) (quotient/remainder m 10))
+            (if (zero? r) 0 (inr-d-p q (* rv r)))])) ; lazy on zero
+  (inr-d-p n 1))
+
+(define (mdr/mp n)
+  (define (inr-mdr/mp m i)
+    (if (< m 10) (values m i) (inr-mdr/mp (digital-product m) (add1 i))))
+  (inr-mdr/mp n 0))
+
+(printf "Number\tMDR\tmp~%======\t===\t==~%")
+(for ((n (in-list '(123321 7739 893 899998))))
+  (define-values (mdr mp) (mdr/mp n))
+  (printf "~a\t~a\t~a~%" n mdr mp))
+
+(printf "~%MDR\t[n0..n4]~%===\t========~%")
+(for ((MDR (in-range 10)))
+  (define (has-mdr? n) (define-values (mdr mp) (mdr/mp n)) (= mdr MDR))
+  (printf "~a\t~a~%" MDR (for/list ((_ 5) (n (sequence-filter has-mdr? (in-naturals)))) n)))