Overlapping, undecidable, incoherent -- or worse?
doc at drjava.de
Thu May 20 15:47:57 EDT 2004
Simon Peyton-Jones wrote:
> As a trivial example, try
> f a = a |= a
> What type shall we infer for f?
> f :: (Bounded a, Enum a, SemiRing a) => a -> a
> f :: (CSemiRing a) => a -> a
This has always confused me - GHC always seems to use the strongest
possible conditions when inferring types (CSemiRing is stronger than PO
because it implies it). Why isn't the type just
f :: (PO a) => a -> a
? Isn't this the most straight-forward (and universal) typing,
especially in the presence of overlapping/undecidable instances?
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