Add Ex 31

31.ml

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+(* Determine whether two positive integer numbers are coprime. (easy)
+
+Two numbers are coprime if their greatest common divisor equals 1. *)
+(*
+	# coprime 13 27;;
+	- : bool = true
+	# not (coprime 20536 7826);;
+	- : bool = true
+*)
+
+let coprime a b =
+	let rec gcd a = function
+		| 0 -> a
+		| b -> gcd b (a mod b) in
+	(gcd a b) = 1;;
+
+coprime 13 27;;
+coprime 20536 7826;;