data-default WAS: [containers] Proposal: Change to the Data.Map Monoid

Starting a new thread to continuing discussing this (I should have done so in the first place). Here's the problem: a class like Default is most useful if everyone's using the same class. The reason is that multiple libraries are all free to reexport the `def` symbol, and they'll all refer to the same identifier. If multiple `def`s exist, then this doesn't work, you need to be careful about *which* `def` you're using, and you may as well just export a default value under its own unique name. I think data-default-generics is overall an improvement on data-default, but the very nature of a fork here makes both packages less useful. I'd much rather that data-default simply merged in data-default-generics. On Wed, May 21, 2014 at 6:12 PM, João Cristóvão wrote:

Sorry for continuing the off-topic, and for promoting a package of mine:

If you only need the class definition, http://hackage.haskell.org/package/data-default-class is a better choice, with no dependencies.

If you prefer a single package with all the dependencies (and with additional generics support), my own fork might be useful: http://hackage.haskell.org/package/data-default-generics

Although I mirrored the original package dependencies, many of which might actually be unnecessary... (given the generics implementation).

Cheers

2014-05-21 15:59 GMT+01:00 Michael Snoyman :

At the risk of veering terribly off-topic... the splitting of data-default

...

into all of those packages caused me a bunch of dependency headaches, most of which I still don't fully comprehend. I miss the good ol' days of a single package.

On Wed, May 21, 2014 at 5:53 PM, Edward Kmett wrote:

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I find myself rather hesitant to recommend that instantiation of the idea ever since it exploded into a half-dozen packages full of orphan instances, but yes.

-Edward

On Wed, May 21, 2014 at 6:38 AM, Herbert Valerio Riedel wrote:

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On 2014-05-21 at 00:23:44 +0200, Andreas Abel wrote:

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> _Lots_ of users initialize empty maps with mempty

Well, this is another issue, empty should be overloaded via

class Empty a where empty :: a

Btw, isn't this what

http://hackage.haskell.org/package/data-default

provides? _______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries

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