Is it possible to convert an effectful function into a IO function to be stored in a data structure?

[newhoggy]

I need to store an IO function that logs in a data type for my logging library to use and it must be derivable from an effectful function:

https://github.com/haskell-works/effectful-zoo/pull/1/files#r1848260662

Is that possible?

Either way, is it the best way for me to do what I'm trying to do?

[ocharles]

You want to use withEffToIO. As to which unlifting strategy, it depends a bit more on how you plan to call these IO actions. Will they be called from the same thread, or different threads?

[newhoggy]

It will initially be the same thread, however the computation could spawn threads itself, and I'd like it to continue to work.

[ocharles]

Ok, then you want to use either the ConcUnlift or ForkUnlift strategies. You would do something like:

withEffToIO (ConcUnlift .. ..) \runInIO -> runInIO do
  -- Your whole app runs here
  foo Foo{ doThing = runInIO thing }

or

runInIO <- withEffToIO ForkUnlift return
...
foo Foo{ doThing = runInIO thing }

I think those are the correct way to use these!

[arybczak]

If it's for logging in multiple threads, ConcUnlift Persistent Unlimited seems like the best option, but generally I wouldn't do it this way and use existing library, either log-effectful or co-log-effectful.

ForkUnlift

It's SeqForkUnlift and thus only for a single thread.

[newhoggy]

Thanks!