Peter Goodspeed-Niklaus

As this description derives directly from that in the problem specifications, I'm transferring the issue there.

Makes sense to me. This repo will be accepting PRs again soon; perhaps create one which implements these suggestions.

Why is this property desirable? Wouldn't the opposite property be better: guarantee that implementations mutate the input, for minimal allocation? Given that property, implementations which need to retain access to...

I'd vote: it's mutable, except if the mutation would change the total set of errors in an exercise. Using your example, I'd expect a Rust test generator to come up...

I haven't used Haskell at all for half a decade, and I was only at a student level even then, so I'm going to attempt to recast this in Rust...

Also, this may be dogshedding, but I'd suggest the title `composite-resistors` instead of `resistor-monoid`; even if these are in fact monoids, calling them that sounds weird in every language I...

> OK, so an implication of that is that your representation of Resistor becomes a function, and composition of resistors becomes function composition. This means that large compositions will cause...

I built a [julia set generator](https://github.com/coriolinus/julia-set) last year for fun; it was in fact a fun exercise, but it took a week. That's more time than I'd typically allocate for...

One thing to mention: if you do add a proc-macro dependency such as either of the crates mentioned above, please make it an optional dependency behind a feature gate (`builders`...

No problem, I did not mean to imply that deriving the builders was mandatory. I can approve once you've addressed the other comments.