bug neither fixed nor listed as known

6 Mar 2002

      Dear Hugs-Bugsers,

As reported in Sep. last year,
there is very serious problem
in hugs when it comes to class
hierarchies. See the program
below. Is anyone maintaining 
hugs and paying attention to 
incoming bug reports?

Thanks,
Ralf

import Monad

class Monad m => C1 m x

-- Monad m is implied by C1 but test diverges if constraint not present
class (C1 m x) => C2 m x
  where
    c2 :: x -> m x

instance Monad m => C1 m Bool
instance C2 Maybe Bool
  where
    c2 = return

test :: Maybe Bool
test = c2 True

-- 
Dr.-Ing. Ralf Laemmel
CWI & VU, Amsterdam, The Netherlands
http://www.cwi.nl/~ralf/
http://www.cs.vu.nl/~ralf/