Re: [Haskell-cafe] Taking over `data-default-*`

Does it make sense to consider stating a law for Default? e.g. if (Monoid t, Default t) then def = mempty On Tue, May 8, 2018 at 11:22 AM Chris Wong wrote:

On Tue, May 8, 2018 at 9:10 PM, Marco Zocca wrote:

...

data-default alone is depended on by > 500 packages : http://packdeps.haskellers.com/reverse/data-default

Could you motivate why it's not a good idea ?

I can think of two reasons:

- It has no laws, so there's formal specification that tells us whether an instance is "correct" or not.

- Type classes are useful when there is a large family of generic operations that can work with them. For example, the utility functions in Control.Monad [1] are used in all kinds of Haskell programs. But there are no such generic operations that apply to all Default instances.

That said -- as you note, it's has quite a few dependents so it's great that someone is stepping up to maintain it regardless.

Chris

[1] https://hackage.haskell.org/package/base-4.11.1.0/docs/Control-Monad.html#g:...

...

On Tue, May 8, 2018 at 11:02 AM, Christopher Allen wrote:

...

Is this something folks still think is a good idea? I purge Data.Default from projects I work on.

On Tue, May 8, 2018 at 3:58 AM, Marco Zocca wrote:

...

Dear all,

I've been increasingly relying on data-default-class, but sadly it doesn't look like it's currently maintained; there are some tickets on the github issue tracker that would need some attention.

I have tried contacting the authro/current maintainer Lukas Mai (CC'd) by email but have not received an answer so far (I hope he's doing well, btw).

This is my first public request for taking over the `data-default` family of packages:

data-default-class data-default-instances-base data-default-instances-containers data-default-instances-dlist data-default-instances-old-locale data-default

Kind regards, Marco Zocca (http://hackage.haskell.org/user/ocramz) _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

-- Chris Allen Currently working on http://haskellbook.com

---

Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- Chris Wong (https://lambda.xyz)

"I had not the vaguest idea what this meant and when I could not remember the words, my tutor threw the book at my head, which did not stimulate my intellect in any way." -- Bertrand Russell _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.