[Haskell-cafe] Re: Improving MTL instances (was: Overlapping/Incoherent instances)

ryani.spam:

On Mon, Oct 13, 2008 at 2:04 AM, J. Garrett Morris wrote:

...

Indeed - MTL seems to have been rewritten at some point in the past to prefer exhaustive enumeration to overlap.

Indeed, and I actually think this is a weakness of the current implementation. Anyone who comes up with a new transformer that provides different functionality than what is there needs to explicitly provide all the relevant instances, instead of letting MonadTrans do its thing.

I just want to make one small point here encouraging people to try out new 'mtl' libraries. There are lots of *new* monad libraries, The new & improved mtl: * monadLib http://hackage.haskell.org/cgi-bin/hackage-scripts/package/monadLib As well as, * mmtl http://hackage.haskell.org/cgi-bin/hackage-scripts/package/mmtl * mtl-tf http://hackage.haskell.org/cgi-bin/hackage-scripts/package/mtl-tf and the huge, * category-extras http://hackage.haskell.org/cgi-bin/hackage-scripts/package/category-extras 'mtl' isn't magic in any way. it isn't distributed with ghc, so we can let the (library) free market pick a winner. Now, if the monadLib guys would advertise their work a bit more effectively... -- Don