https://github.com/noredink/list-selection

A list with a selected item. Like a zipper, but optional.
https://github.com/noredink/list-selection

Last synced: about 2 months ago
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A list with a selected item. Like a zipper, but optional.

• Host: GitHub
• URL: https://github.com/noredink/list-selection
• Owner: NoRedInk
• License: bsd-3-clause
• Created: 2017-07-13T19:18:18.000Z (over 7 years ago)
• Default Branch: master
• Last Pushed: 2018-08-30T20:15:25.000Z (over 6 years ago)
• Last Synced: 2024-05-08T23:24:39.593Z (8 months ago)
• Language: Elm
• Homepage: http://package.elm-lang.org/packages/NoRedInk/list-selection/latest
• Size: 42 KB
• Stars: 10
• Watchers: 6
• Forks: 5
• Open Issues: 4
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

        
# Selection List [![Build Status](https://travis-ci.org/NoRedInk/list-selection.svg?branch=master)](https://travis-ci.org/NoRedInk/list-selection)

Create a list which may have one (but no more than one) item selected.

You can never select an item that isn't in the list.

Selections are optional, so this is slightly different than a zipper.

## Usage

Create a Selection list from a regular list by using `fromList`.

Let's use this to choose what we'd like for lunch.

```elm

import List.Selection exposing (Selection)

type Lunch

    = Burrito

    | ChickenWrap

    | TacoSalad

    | DonerKebab

todaysMenu : Selection Lunch

todaysMenu =

    [ Burrito, ChickenWrap, TacoSalad ]

        |> List.Selection.fromList       -- create a new Selection list

        |> List.Selection.select Burrito -- now let's see, I think I'd like a burrito (yum, monads!)

```

Since I already chose what I want for lunch, I can get it with `selected`:

```elm

List.Selection.selected todaysMenu -- `Just Burrito`

```

But what if you try and select something that doesn't exist in the list?

The shop was out of doner kebab today, but what if we ask for it?

```elm

todaysMenu

    |> List.Selection.select DonerKebab -- this doesn't exist in our menu, so...

    |> List.Selection.selected          -- `Just Burrito` (selection unchanged)

```

And if I change my mind, I can remove my choice with `deselect`:

```elm

todaysMenu

    |> List.Selection.deselect -- deselect any current selection

    |> List.Selection.selected -- `Nothing`

```

## Developing

Install Elm and `elm-test` and `elm-verify-examples` from NPM, then run `make` to run tests and generate documentation.

## License

Licensed under a BSD 3-Clause license