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

[Iavor Diatchki]

Hello,
The currently released version of monadLib does not use overlapping
instances, indeed.
However, in the monadLib  repo (http://github.com/yav/monadlib) there
is a file called "MonadLib4.hs" which contains a version of the
library that is implemented with overlapping instances, so you can
play around with it.  I'd be interested to get feedback on this
version of moandLib.
-Iavor

On Mon, Oct 13, 2008 at 12:44 AM, J. Garrett Morris
<jgmorris at cecs.pdx.edu> wrote:
> 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.
>
>  /g
>
> --
> I am in here
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