Data commit

Task/Middle-three-digits/OCaml/middle-three-digits.ocaml

@@ -0,0 +1,25 @@
+let even x = (x land 1) <> 1
+
+let middle_three_digits x =
+  let s = string_of_int (abs x) in
+  let n = String.length s in
+  if n < 3 then failwith "need >= 3 digits" else
+  if even n then failwith "need odd number of digits" else
+  String.sub s (n / 2 - 1) 3
+
+let passing = [123; 12345; 1234567; 987654321; 10001; -10001; -123; -100; 100; -12345]
+let failing = [1; 2; -1; -10; 2002; -2002; 0]
+
+let print x =
+  let res =
+    try (middle_three_digits x)
+    with Failure e -> "failure: " ^ e
+  in
+  Printf.printf "%d: %s\n" x res
+
+let () =
+  print_endline "Should pass:";
+  List.iter print passing;
+  print_endline "Should fail:";
+  List.iter print failing;
+;;