[Haskell-cafe] What to call Occult Effects

[David Feuer]

Ah, you're right. I wrote that while recovering from a migraine, and it was
bogus!

On Wed, Nov 11, 2020, 11:57 PM Viktor Dukhovni <ietf-dane at dukhovni.org>
wrote:

> On Wed, Nov 11, 2020 at 09:47:43PM -0500, David Feuer wrote:
>
> > If m is occlusive, so is ReaderT e m:
> >
> > [...]
> >
> > I believe this works for StateT as well.
>
> I am puzzled what you mean by that, given that
>
>     State s a = StateT s Identity a
>
> and while "Identity" is "occlusive", State is not.
>
>     λ> import Control.Monad
>     λ> import Control.Monad.Trans.State.Strict
>     λ> runState (liftM2 (const id) (put True :: State Bool ()) get) False
>     (True,True)
>     λ> runState ((const id) (put True :: State Bool ()) get) False
>     (False,False)
>
> --
>     Viktor.
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