I am strongly against deprecating ExistentialQuantification and prefer it
over the GADT notation for non-GADT datatypes. I find GADT notation nice
when the types of the result change, but I don't think it is great for
normal types (which are the large majority of types I use) for these
reasons:
- It duplicates the declaration of the types many types, but often it is
not obvious that you have the same type
- The disconnect between the type variables in the data declaration and
the constructors is confusing, which is why I prefer the GADT from where
you declare the kind of the GADT, but that's quite ugly and verbose.
On Fri, Dec 4, 2020 at 7:25 AM Joachim Breitner
Hi,
Am Freitag, den 04.12.2020, 15:47 +0100 schrieb Spiwack, Arnaud:
I'm just saying: let's _not_ add ExistentialQuantification in GHC2021 (because it ought, in my opinion, to be considered deprecated).
I’m convinced!
Let's not go into talking about chopping the feature into smaller pieces.
Not for GHC2021! But if GADTs don’t make it this round, we can ask the question if ExistentialVariables is a feature worth having on its own, of if anyone who wants to use that should just go for GADTs.
Cheers, Joachim
-- Joachim Breitner mail@joachim-breitner.de http://www.joachim-breitner.de/
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