That's why I use a counter as a simple demo - you see state changing with each call and it's done without using a global or passing in some kind of context obje

That's why I use a counter as a simple demo - you see state changing with each call and it's done without using a global or passing in some kind of context object. It's not a lot more powerful than the adder, but in my experience it more often generates a "what the hell..." kind of reaction to the uninitiated.