Data commit

Task/Happy-numbers/Racket/happy-numbers.rkt

@@ -0,0 +1,22 @@
+#lang racket
+(define (sum-of-squared-digits number (result 0))
+  (if (zero? number)
+      result
+      (sum-of-squared-digits (quotient number 10)
+                             (+ result (expt (remainder number 10) 2)))))
+
+(define (happy-number? number (seen null))
+  (define next (sum-of-squared-digits number))
+  (cond ((= 1 next)
+         #t)
+        ((memq next seen)
+         #f)
+        (else
+         (happy-number? next (cons number seen)))))
+
+(define (get-happys max)
+  (for/list ((x (in-range max))
+             #:when (happy-number? x))
+    x))
+
+(display (take (get-happys 100) 8)) ;displays (1 7 10 13 19 23 28 31)