On 2008 Jul 5, at 19:02, Neil Mitchell wrote:
This is either a GHC bug, or a Yhc+Hugs bug - I'm not sure which, but the compilers disagree:
import Prelude hiding ((==)) data Foo = Foo instance Eq Foo where (==) a b = True
I was thinking that GHC's behaviour seems more sensible, but the following fails:
import qualified Module as M
instance MClass Foo where M.foo = undefined
M. is not allowed as a prefix of a function, which makes resolving ambiguities hard unless the compiler solves the issue for you (as Hugs and Yhc do)
But this works for me in ghc: foo.hs:
import Mod as M
data Bar a = Bar Int a
instance M.MClass (Bar a) where foo _ = M.foozero foozero = Bar 0 (undefined :: a)
main = putStrLn "foo"
Mod.hs:
module Mod where
class MClass a where foo :: a -> a foozero :: a
-- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH