GADTs and pedagogy was Re: GADTs and fundeps

Abraham Egnor abe.egnor at
Fri Apr 8 12:13:30 EDT 2005

> > You mean, if the data type being defined doesn't actually use the
> > generality of GADTs, allow GADT syntax, and deriving() too?
> Yes, that would be very nice for the HaskellDemo and new users.
> I'd definitely switch all of my non-GADT datatypes to use that.

One worry I have about this is that it'll introduce a new tripwire
that new users will have to watch out for - if they use GADT notation
for all data defintions, eventually they'll pass the threshold beyond
which deriving() mysteriously doesn't work, probably without even
knowing they're doing anything different.


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