Should this class have a detail::SeiveImpl which has the implementation, and the public API be class Seive :: public detail::SeiveImpl?

I'm still thinking through how to hide the common/utilities stuff, and whether we should. This Seive is used internally in one place so far and it might be that we just end up making it internal. For now, though I don't think it should affect this PR.

(I'd love to gather your thoughts on the utilities as well)

I think whether it's an internal or external common/utility source, the consistency of having the implementation hidden in detail helps a developer to know where, if ever, they need to look for source code of implementation. The API again just being a contract whether it's internal or external.

The benefit to hiding internals such as what we've been doing is so that we make a contract with the outside world and know that if we don't break that contract, consumers should be able to build against RAFT. I'm less concerned internally because we will get build errors when things change. I think there is still a level of caution that we can take, but it's not going to require we protect the contract as strongly as w/ the public (external) APIs.

The problem with many of these files w/ utility functions is that there are no "internal" bits- the functions themselves are all external so we don't gain as much by hiding those bits. This is my perspective anyways. I'm still undecided on exactly what we should do. One part of me thinks we should eventually copy the public utils stuff into a raft/utils directory and deprecate the old ones and call it a day. I think we should revisit after moving over the primitives, since those are more of the core focus.

Sounds good. It of course doesn't matter much when it's just an internal function, and my only point as a dev was that I would know where to find the implementation if I had to.

Apart from that, I'm fully onboard for the raft/utils package. The utils in the root directly are a bit of a mess and they can be cleaned significantly. But yes, not the highest priority!