Stack overflow

[Alain Cremieux]

Hi,

The following code compiles OK with hugs (dec 2001) but produces a loop
& stack overflow with GHC 5.04

data Ctx m a b = forall i. CBCC  (a -> CUT m i -> CUT m i) (CUT m i)
(Ctx m i b)
newtype CUT m a   = MkCut (forall b. Ctx m a b -> m b)

promote :: Monad m => m a -> CUT m a
promote m          = MkCut (\ctx0 -> case ctx0 of
                                          CBCC c f ctx  -> m >>= (\a ->
let MkCut q = c a f

in  q ctx))


when I replace the 'newtype' by 'data', it compiles again with GHC

- the code is taken (and simplified) from "Deriving Backtracking Monad
Transformers" from Ralph Hinze
- compiled with -fglasgow-exts (of course), Linux and Windows versions
of GHC and GHCI 5.04

Alain