You’re right in the general case. My language does not have mutation, so refcounting is[1] just an optimisation to avoid copying and allow in-place mutation whe

You’re right in the general case. My language does not have mutation, so refcounting is[1] just an optimisation to avoid copying and allow in-place mutation when the refcount is 1; it only applies to boxed values. I should have said “copy on write”. And I’m well aware of modern GC implementations, but one of my goals is deterministic memory behaviour, a feature lacking in other functional languages. I swear I know what I’m doing. :) [1]: Read: will be; the current implementation is interpreted but I’m working with a friend on an x86_64 VM target.