Provide a function that takes an ST computation that returns an STArray, and returns an Array, without any copying

[no-longer-on-githu-b]

This is perfectly safe, due to state thread scopes, yet currently the docs suggest that people use unsafeFreeze manually.

[hdgarrood]

The current runSTArray is deprecated because the open effect row means that you can do things like saving the mutable reference in a Ref, which makes it unsafe. I wouldn't mind un-deprecating it if we changed its signature at the same time to use a closed row, like this:

runSTArray :: forall a h. (forall h. Eff (st :: ST h) (STArray a)) -> Array a

See #87 and #89 for how we ended up at the current design.

[hdgarrood]

Although in that case a better name might be pureSTArray, like with pureST.

[no-longer-on-githu-b]

If you unsafeFreeze an STArray from a pureST, you can still mutate it from a deferred Aff action, because launchAff introduces no effects other than EXCEPTION, which can be removed

[hdgarrood]

I wonder if that's really a problem with Aff's API...

[natefaubion]

I wonder if that's really a problem with Aff's API...

It is. Scheduling is an effect. So either runAff needs to introduce an ASYNC effect, or delay should introduce an effect. All other scheduler type things (like setTimeout) have their own effect.

[hdgarrood]

I'm actually beginning to wonder, in discussions like these, whether it would make sense to make the fact that ST is based on Eff an implementation detail; to use a newtype over Eff so that Eff doesn't appear in any of the type signatures exported by this library.

[natefaubion]

purescript/purescript-st#8