Data commit

Task/Van-Eck-sequence/Racket/van-eck-sequence.rkt

@@ -0,0 +1,16 @@
+#lang racket
+(require racket/stream)
+
+(define (van-eck)
+  (define (next val n seen)
+    (define val1 (- n (hash-ref seen val n)))
+    (stream-cons val (next val1 (+ n 1) (hash-set seen val n))))
+  (next 0 0 (hash)))
+
+(define (get m n s)
+  (stream->list
+   (stream-take (stream-tail s m)
+                (- n m))))
+
+"First 10 terms:"          (get 0     10 (van-eck))
+"Terms 991 to 1000 terms:" (get 990 1000 (van-eck)) ; counting from 0