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

J. Garrett Morris jgmorris at cecs.pdx.edu
Mon Oct 13 03:44:06 EDT 2008

On Mon, Oct 13, 2008 at 12:29 AM, Ryan Ingram <ryani.spam at gmail.com> wrote:
> Of course, the point of this message isn't just to complain.  The
> overlap implementation was abhorrent and it *is* better now than it
> was before.

I'm curious what you find abhorrent about the overlap implementation
that was there before - in particular, it seems like it was designed
to handle both the combinatorial explosion and the corner cases you
mentioned.  Did you find writing the MonadTrans instances unpleasant?
Was it the presence of overlapping instances at all?

On Mon, Oct 13, 2008 at 12:35 AM, Don Stewart <dons at galois.com> wrote:
> I just want to make one small point here encouraging people to try out
> new 'mtl' libraries. There are lots of *new* monad libraries,

Without knowing better myself: do any of these libraries address the
issue Ryan's brought up?  I know that monadLib takes the same approach
the MTL does to this, and so is likely to have the same difficulties.


I am in here

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