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

Krasimir Angelov kr.angelov at gmail.com
Thu May 22 15:52:11 EDT 2008

Hello Guys,

We have Data.Tree in the standard libraries for a long time but for
some reason we still don't have standard implementation for Zipper. I
wrote recently one implementation for Yi but there are many other
versions hanging around. At least I know for some. I propose to add
one in the standard libraries i.e. the "containers" package. The
version that I use currently is here:


If you would like to do code review I will be happy to hear comments.
After the API is settled down I will write test cases also. One thing
that is worying me is that the current version uses State monad which
is in the "mtl" package while the natural place for Data.Tree.Zipper
is in "containers". This will create an extra dependency. Is this


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