MultiwayTreeZipper

This library was created with the goal of allowing a multiway tree to be navigated and updated.

I ran into the problem when designing a tree UI control to use with The Elm Architecture. I realized that to keep track of the state in the model for things like whether a node is selected or expanded, I needed a way to update specific nodes through actions.

There will be more examples to come, but this is meant as a library to solve a piece of the puzzle, which will be used with others to create a Tree UI control

Run tests (from a cloned repo)

npm install -g elm
cd tests
elm-package install -y
elm-make Tests.elm --output tests.js
node tests.js

NOTE: elm-test Tests.elm -c elm-make.cmd might have to be used if running on Windows.

Looking for Elm 0.19?

I upgraded to the latest version of elm in a separate branch due to changes to both how dependencies are managed and tests are performed. That code lives in the elm-0.19-upgrade branch, and has been deployed to Elm Packages as version 1.10.3.

The API did not change, however, the custom operator that was demonstrated in docs and the tests, (&>) can no longer be used as of 0.19. I updated both to use the best concise alternative I could, which uses|> Maybe.andThen and partial application. See the test for an example!