tomjkidd / elm-multiway-tree-zipper

A library for navigating and updating immutable trees.

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!

elm-multiway-tree-zipper's Issues

Documentation code snippets incompatible with Elm 0.18.0 in version 1.10.1

The &> infix operator as defined doesn't work as expected because Maybe.andThen params are reversed in 0.18.0.

(Haven't verified this. Expectation based on experience upgrading this module to Elm 0.18.0.)

Multiple cursors support

Hi! Don't you plan to add support for a zipper with multiple cursors, like described here?

I'm currently trying this package out to manage nodes selections in a tree, and I aim to provide multiple selections over time.

If you don't plan to implement this, probably you could direct me to some article or book where I can find more practical instructions on implementing such a thing. Where did you get the basis during your work on this library?

indexedMap doesn't need to return a Maybe

Since mapListOverTree only returns Nothing if its list is empty, indexedMap builds a list based on the length of the tree, and a multiway tree always has at least one node I don't think there is any way for indexedMap to actually return Nothing.

Update tests to elm 0.19