restructure + lecutre 07

lectures/07/counter.ml

@@ -0,0 +1,7 @@
+let counter =
+  let c = ref 0 in
+  (fun () -> incr c; !c);;
+
+let make_counter init =
+  let c = ref init in
+  (fun () -> let x = !c in incr c; x);;