Initial data commit

Task/Arithmetic-Rational/OCaml/arithmetic-rational-3.ocaml

@@ -0,0 +1,21 @@
+(* interface *)
+module type RATIO =
+   sig
+     type t
+     (* construct *)
+     val frac : int -> int -> t
+     val from_int : int -> t
+
+     (* integer test *)
+     val is_int : t -> bool
+
+     (* output *)
+     val to_string : t -> string
+
+     (* arithmetic *)
+     val cmp : t -> t -> int
+     val ( +/ ) : t -> t -> t
+     val ( -/ ) : t -> t -> t
+     val ( */ ) : t -> t -> t
+     val ( // ) : t -> t -> t
+   end