Data update

Task/Digital-root/OCaml/digital-root.ml

@@ -0,0 +1,16 @@
+let rec digit_sum b n =
+  if n < b then n else digit_sum b (n / b) + n mod b
+
+let digital_root b n =
+  let rec loop a x =
+    if x < b then a, x else loop (succ a) (digit_sum b x)
+  in
+  loop 0 n
+
+let () =
+  let pr_fmt n (p, r) =
+    Printf.printf "%u: additive persistence = %u, digital root = %u\n" n p r
+  in
+  List.iter
+    (fun n -> pr_fmt n (digital_root 10 n))
+    [627615; 39390; 588225; 393900588225]