Fwd: [Haskell-cafe] Data.Tree.Zipper in the standard libraries

Iavor Diatchki iavor.diatchki at gmail.com
Wed Jun 4 13:14:59 EDT 2008

If this is the consensus, than people that feel this way should write
a document describing the new process so that we know how to
contribute code.  Based on the current sentiments, we should decide at
least on the following:

- what is a "core" package
  Perhaps, a package that is distributed with GHC? But then, we should
be having this discussion on the GHC users list... Also, was not the
whole point of splitting the base library, so that we can gain the
freedom to update libraries independent of implementations?

- what constitutes a "significant" change
  Not sure how to define this.  I would be weary of changes to the
existing functions/types in the APIs of existing modules.  But adding
extra functionality?  Especially, if---like in the case of
Zipper---the implementation can be more or less computed from an
existing definition in the package (I am referring to the fact that
the zipper is the derivative of Tree, for details you can look at
Conor's paper).

- what makes code "proven"
  Again, not sure how to define this.  The code for Zipper has QC
tests that cover it 100%, according to HPC.  Of course, this does not
mean that it is perfect, but certainly should give us some assurance
that it works.  Does code have to sit on hackage for a certain amount
of time, before it can be added to the libraries?  Or are we going to
require that it is already used by many people as a separate package,
and then we are going to ask everyone to change their code, so that
they can start using it from the new location?  Neither option seems
very nice.

But more to the point though, does anyone have any suggestions about
what may be wrong with the Zipper concretely, rather then the library
process in general?  Neil, the sniplet that you posted from the IRC
channel does not give us an idea of what we might want to change.


On Wed, Jun 4, 2008 at 2:39 AM, Malcolm Wallace
<Malcolm.Wallace at cs.york.ac.uk> wrote:
> Duncan Coutts <duncan.coutts at worc.ox.ac.uk> wrote:
>> I would tend to agree with Neil that significant additions to the core
>> libraries should be proven first as separate packages and integrated
>> later.
> +1
> Regards,
>    Malcolm
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