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: http://code.haskell.org/yi/Data/Tree/Zipper.hs 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 acceptable? Regards, Krasimir