[Haskell-cafe] Re: Optimization problem
ctm at Cs.Nott.AC.UK
Tue Sep 19 08:52:02 EDT 2006
apfelmus at quantentunnel.de wrote:
> Btw, why are there no irrefutable patterns for GADTs? I mean, such a sin
> should be shame for a non-strict language...
> data Eq a b where Refl :: Eq a a
> coerce :: Eq a b -> a -> b
> coerce ~Refl a = b
coerce undefined True :: String
Bang you're dead. Or rather... Twiddle you're dead.
Moral: in a non-total language, if you're using indexing to act as
evidence for something, you need to be strict about checking the
evidence before you act on it, or you will be vulnerable to the
blandishments of the most appalling liars.
As Randy Pollack used to say to us when we were children, the best thing
about working in a strongly normalizing language is not having to
All the best
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