restructure + lecutre 07

lectures/05/ref.ml

@@ -0,0 +1,12 @@
+(* we can impliment our own ref type *)
+type 'a ref = { mutable contents: 'a };;
+
+(* reference and dereference implimentation *)
+let ref x = { contents = x };;
+let (!) r = r.contents;;
+
+(* assign to a mutable field *)
+let (:=) r x = r.contents <- x;;
+
+let incr r = r.contents <- r.contents + 1;;
+let decr r = r.contents <- r.contents - 1;;