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

[Chris Wong]

On Tue, May 8, 2018 at 9:10 PM, Marco Zocca <zocca.marco at gmail.com> 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:4


>
> On Tue, May 8, 2018 at 11:02 AM, Christopher Allen <cma at bitemyapp.com>
> 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 <zocca.marco at gmail.com>
> 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 at haskell.org
> >> http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
> >
> >
> >
> > --
> > Chris Allen
> > Currently working on http://haskellbook.com
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-- 
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
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