Hello Wei,
Thursday, May 8, 2008, 11:10:08 PM, you wrote:
> test :: a -> Int -> a
> shift is defined as "a -> Int -> a"
not exactly ;) this type signature is given inside class Bits, where
'a' isn't a free variable (as in standalone signature declaration),
but means 'a' from type class header:
class Num a => Bits a where
shift :: a -> Int -> a
so, this declaration is equivalent to the following standalone one:
shift :: (Bits a) => a -> Int -> a
from the common sense POV, you can't shift *ANY* type 'a', but only
types that belong to the Bits class. so, shift cannot have signature
w/o class, and the same remains true for `test`
--
Best regards,
Bulat mailto:[EMAIL PROTECTED]
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