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

[Duncan Coutts]

On Sun, 2008-06-01 at 12:49 -0400, Isaac Dupree wrote:
> Neil Mitchell wrote:
> > Hi Krasimir,
> > 
> > What is the strong justification for adding this to the base library?
> > Is there some particular reason that it can't be done outside of base,
> > or is there some particular need that makes this code desirable in the
> > base libraries? Could it be added as a separate library on hackage,
> > worked on for a while, and then merged into the base latter if
> > appropriate?
> 
> 'containers', not 'base'.  But still, I think it should stay in a 
> separate package.  Someday Data.Tree may be removed from the more-used 
> containers too.  (do we know who does use Data.Tree, btw?)

It's used ad-hoc in lots of programs whenever people want a rose-tree.
It's convenient to have and as Ross says it's used in the public
interface of Data.Graph. If anything I think it should be extended. For
example where is the post-order flattening, the all-paths etc. There are
useful operations defined for it in Data.Graph that should be moved to
Data.Tree itself.

Duncan