New type of ($) operator in GHC 8.0 is problematic

Christopher Allen cma at
Tue Feb 16 00:35:29 UTC 2016

I don't think it's a good idea to create a dumbed down Prelude and existing
resources not covering what programmers need to know in order to actually
use Haskell as everyone else uses it is much of the reason I had to write a
book to begin with. This type isn't just noise for beginners, it's noise
for practitioners too. Consider what I said earlier about a 15 year user of
Haskell finding the type confusing and irrelevant.

There are a couple good proposals for addressing levity polymorphism
leaking into the type. I think the one Ben Gamari had in mind that I
thought would be fine is waiting for a patch.

On Mon, Feb 15, 2016 at 6:30 PM, Manuel M T Chakravarty <
chak at> wrote:

> > Ben Gamari <ben at>:
> > builds. In effect the message to users would be,
> >
> >    "yes, unboxed types exist and they are now on sound theoretical
> >    footing, but they are still largely an implementation detail, just as
> >    they have always been. If you want to use them you need to know
> >    where to look."
> >
> > Perhaps this can be revisited at some point in the future when we have a
> > better story for a beginner's Prelude but for now I'm not sure we want
> > to subject everyone to these new types.
> >
> > Anyways, this is just my two cents. It would be nice to hear what others
> > think.
> Sounds like a good plan to me.
> Manuel
> _______________________________________________
> ghc-devs mailing list
> ghc-devs at

Chris Allen
Currently working on
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