bug neither fixed nor listed as known
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/
Hi,
he's just being overly modest not to relay the good news
himself, but one Sir Jeffrey Lewis has just committed a TC
change which fixes this. Thanks for reporting it.
--sigbjorn
----- Original Message -----
From: "Ralf Laemmel"
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/
participants (2)
-
Ralf Laemmel -
Sigbjorn Finne