Am Samstag 20 Juni 2009 03:51:08 schrieb Dan Doel: > On Friday 19 June 2009 9:43:29 pm Scott Michel wrote: > > wombat :: (IArray UArray e, Ix ix, MArray (STUArray s) e (ST s)) => e > > -> ix -> UArray ix e -> UArray ix e > > wombat val idx mem = (unsafeThaw mem :: ST s (STUArray s ix e)) >>= > > (\mmem -> unsafeFreeze mmem) > > Based on the error message and dealing with this sort of thing before, your > problem is that when you say: > > ":: ST s (STUArray s ix e)" > > the s, ix and e there aren't the same as they are in the signature of > wombat. To make them the same, you need the ScopedTypeVariables extension, > and to make wombat's signature: > > wombat :: forall e ix s. ... > > where the dots are your current signature. > > It's possible you'll still have errors, but that will solve the one in your > mail. > > -- Dan
No, only part of it. Another part is unsafeFreeze :: (Ix i, MArray a e m, IArray b e) => a i e -> m (b i e) so unsafeThaw arr >>= unsafeFreeze lives in a monad, here (ST s) and to get the type he wants, he has to wrap it in runST. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
