@samdphillips yeah the whole “mutability” thing is a challenge in Racket. It hurts me inside. But I’m keeping the intcode in a mutable vector and that seems to work.

A global mutable vector. Ick.

Check that, it’s local to the handler. phew.

You will need to change from a mutable vector to something else on Day 9, but it should be a straightforward change :slightly_smiling_face:

I just doubled the size of the vector :shrug: