> I personally find it can make the code easier to understand, like you say, but it seems like you're getting a lot of disagreement from the other comments.

The disagreement they're getting is not on the use of immutability and pure transformations, it's on the fantasy that a "sufficiently smart compiler" would be able to optimise this (especially non-trivial versions of this) into mutations under the cover.

Furthermore, V is apparently supposed to be a fairly low-level language, if you have to rely on the compiler to perform the optimisation, can't statically assert that it does so[0] and it fails to, that is extremely costly in both "machine" time and "programmer" time (as you'll start wrangling with the compiler's heuristics to finally get what you need).

If you want immutability, do it, but do it properly: build the runtime and datastructures[1] and escape hatches which make it cheap and efficient, don't handwave that the compiler will solve the issue for you.

[0] and if you are you may be better off just adding mutation to the language already

[1] non-trivial immutable data structures are tree-based and translate to a fair number of allocations, you really want an advanced GC