Rewrite Free monads to Effectful

FPtje commented 1 year ago

Description

This (somewhat large) PR rewrites Hoff from using effects to using effectful. This is mostly an exercise for me to personally get familiar with the library, but I think it's worth considering a merge.

Why prefer `effectful` over free monads?

Hoff uses Free monads quite well, which makes it a perfect example for comparison against effectful. In that comparison, I think effectful comes out on top:

Effects are more easily composable, no hassling with the Sum tree structure to combine different effects
No hassle with the continuation passing style. This may be a minor point, but being able to remove all those conts in the code was very satisfying
Very clear documentation, with very practical examples
Performance, though I should note that in my experience, Hoff has never had performance problems. I'm relying on the benchmarks in the documentation for this one.
It's about the same amount of code. As of writing, the effectful implementation only has 30 more lines in total. In some places effectful is more boilerplate, in other places free has more.

Why rewrite?

Under normal circumstances, I would argue quite strongly that rewriting is a bad idea. In this case, this is a Hobby project, one that I would also like to use to advocate for the effectful library, and to teach the differences between free and effectful. The really nice thing here is that this is a PR where the left side shows all the implementation specifics of free, and the right side shows that of effectful.

For this purpose I will also write a bunch of review comments. This documents the differences, and also makes the job of a reviewer easier.

Testing

This PR has been tested as follows:

Ran unit tests
Ran the executable, queried metrics, used the scripts in tools/ to merge a PR in a git-sandbox repository

Since semantics didn't change, and above tests passed the first try, I'm confident this PR will not negatively affect Hoff's performance.

FPtje commented 1 year ago

Thanks everyone for the review! Let's merge!

@OpsBotPrime merge

OpsBotPrime commented 1 year ago

Pull request approved for merge by @FPtje, rebasing now.

OpsBotPrime commented 1 year ago

Rebased as fc89ccd788334f2c56212d4ef3d4e9fe1acc845c, waiting for CI …

OpsBotPrime commented 1 year ago

CI job :yellow_circle: started.

channable / hoff