[Haskell-cafe]  == 
ekirpichov at gmail.com
Fri May 29 05:51:10 EDT 2009
2009/5/29 Paul Keir <pkeir at dcs.gla.ac.uk>:
> Hi all,
> GHC is not happy with this:
> f =  == 
This fails because GHC doesn't know which 'a' you mean, and can't
choose an Eq instance.
> nor this:
> f' = (::(Eq a) => [a]) == (::(Eq a) => [a])
This fails for the same reason.
> but this is OK:
> f'' = (::[Integer]) == (::[Integer])
> GHCI is comfortable with  == , so why not GHC? 'Just curious.
Because GHCI has some 'default' instances, whereas GHC doesn't. This
time, it probably chooses a=().
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