Realized after posting that I could have used an exploding lambda to initialize the memory. It's a bit prettier.

I like this way of programming, it feels like ascii physics. The replacement steps shows my little cursor `>` moving across the cons cells until it collides with (), and then bounces back out of the list. It's like Orca, there's no hidden state, everything that relates to the evaluation has to be present in the source, pausing the evaluation at any moment yields a valid program.