Switch from Eff to IO

[paf31]

Optimizer rules need to be updated as part of the switch to IO as the default effect monad.

[Pauan]

Woah woah woah woah, PureScript is getting IO instead of Eff? When did this happen?

[michaelficarra]

@Pauan It was done via emoji-based Twitter poll — the most appropriate medium for language design discourse.

[Pauan]

@michaelficarra Thanks for the link.

That's great news! I always really liked the idea of Eff, but I hated the implementation:

1. So many unintuitive errors for things which should work.

2. Eff is always a 0-argument JS function, which means you can't have different implementations for different effects.

[paf31]

Actually, it's been discussed in several other places before that, including on Slack, and on the eff repo, including an unmerged PR for a previous version. I think the eff repo is the right place to discuss it if there are objections, but this is the issue to track the necessary compiler changes. The Twitter poll was just one more check I wanted to do to see how the broader community (who might not watch all of the repos) might respond to the change.

[garyb]

Should we have a real issue about the name of Eff vs IO? I think a couple of threads on Slack about it means people's voices on it may be easy to miss. I was there for the first discussion that Phil wasn't, and it seemed like the consensus of having Eff :: Type -> Type was much preferable to renaming to IO, but then I saw the tail end of a Slack conversation the other day where the reverse seemed to be the case.

[paf31]

Yes, sounds like a good idea.

[maddie927]

I don't know much of the background on this, but Eff e a -> Eff a seems like a much better way to go if everything currently using Eff and Aff should be removing its effect rows. IO seems better if there's still a use case for keeping the current Eff implementation around (no idea what that would mean for Aff). I'd prefer modifying Eff and Aff in that case, because it basically keeps things working the way they are, just easier to work with. Converting to IO seems confusing from a dependency perspective (ex: pulling in 3 libraries and each use a different version of IO/Eff).

[garyb]

I'm slightly more in favour of keeping the Eff name and dropping the row than renaming to IO too. I could get used to it either way, but it definitely seems like the update overhead will be lower by continuing with Eff / Aff.

[hdgarrood]

Let’s discuss what we call it in purescript-deprecated/purescript-eff#25 perhaps?

[garyb]

Sure, I'll port the comments over.

[starper]

+1 for having base IO a and Eff e a as an extended version of IO a