Hobby-hacking Eric


rose zipper on hackage

I guess this isn't big enough to go on the haskell@ mailing list: I have uploaded Krasimir Angelov and Iavor S. Diatchki's Data.Tree implementation of zippers onto hackage. The package is called rosezipper and it is available under the BSD3 license.

For the interested, "The Zipper is an idiom that uses the idea of “context” to the means of manipulating locations in a data structure." (Haskell wiki).

For me, zippers are just a very nice way to navigate and edit trees. By "nice", I mean elegant, efficient and purely functional. Before learning about zippers, I only knew how to navigate trees from top to bottom, but if I wanted to go back up a node, or visit a sibling node, I basically had to start over from the root. Zippers allow me to walk the tree in any direction, visiting a node's parent, children and siblings without starting over from the top. This kind of thing is especially handy for Natural Language Processing people, basically, anybody who eats trees for a living.

If you would like to learn more, I would recommend Apfelmus's very friendly tutorial (part of the Haskell wikibook).

Thanks to Krasimir and Iavor for implementing this and for allowing me to package it up.

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