# xElm
[![build status](https://travis-ci.org/exercism/xelm.svg?branch=master)](https://travis-ci.org/exercism/xelm)

Exercism Exercises in Elm

## Setup

The simplest way to install Elm is via Node.js/NPM.

If you don't already have Node.js installed on your computer, you can download it from [the official site](https://nodejs.org/). Once you have Node.js up and running, follow these steps to install the Elm platform and elm-test.

```bash
$ npm install --global elm elm-test
```


## Contributing

Thank you so much for contributing! :tada:

Please start by reading the general Exercism [contributing guide](https://github.com/exercism/x-api/blob/master/CONTRIBUTING.md#the-exercise-data).

We welcome pull requests that provide fixes and improvements to existing exercises. If you're unsure, then go ahead and open a GitHub issue, and we'll discuss the change.

Please keep the following in mind:

- Pull requests should be focused on a single exercise, issue, or change.

- We welcome changes to code style, and wording. Please open a separate PR for these changes if possible.

- Please open an issue before creating a PR that makes significant (breaking) changes to an existing exercise or makes changes across many exercises. It is best to discuss these changes before doing the work.

- Follow the coding standards found in [The Elm Style Guide](http://elm-lang.org/docs/style-guide). Please consider running [elm-format](https://github.com/avh4/elm-format) before submitting a pull request.

- Watch out for trailing spaces, extra blank lines, and spaces in blank lines.

- Each exercise must stand on its own. Do not reference files outside the exercise directory. They will not be included when the user fetches the exercise.

- Exercises should use only the Elm core libraries.

- Please do not add a README or README.md file to the exercise directory. The READMEs are constructed using shared metadata, which lives in the
[exercism/x-common](https://github.com/exercism/x-common) repository.

- Each exercise should have a test suite, an example solution, a template file for the real implementation and an `elm-package.json` file with the `elm-test` and `elm-console` dependencies. The CI build expects files to be named using the following convention. The example solution should be named `ExerciseModuleName.example`. The template file should be named `ExerciseModuleName.elm`. Test file should be named `ExerciseModuleNameTest.elm`.

- The recommended workflow when working on an exercise is to first create the implementation and test files, `ExerciseModuleName.elm` and `ExerciseModuleNameTest.elm`.
  - Test the new exercise directly by running `elm-test exercises/exercise_module_name/ExerciseModuleNameTest.elm`.

  - Once the implementation of the exercise is complete, move `ExerciseModuleName.elm` to `ExerciseModuleName.example` and create the template file.

  - Make sure everything is good to go by running all tests with `bin/build.sh`.

  - If you have [elm-format](https://github.com/avh4/elm-format) installed, you can easily check the project by running `WITH_FORMAT=true bin/build.sh`. If you get diffs on exercises other than the one you are working on, please submit a separate pull request.

- Please do not commit any Elm configuration files or directories inside the exercise, such as `elm-stuff`. Please include only the standard `elm-package.json`.

- Test files should use the following format:

```elm
port module Main exposing (..)

import Test.Runner.Node exposing (run)
import Json.Encode exposing (Value)
import Test exposing (..)
import Expect


tests : Test
tests =
    describe "Bob"
        [ test "first test" <|
            \() ->
                True
                    |> Expect.equal True
        , test "second test" <|
            \() ->
                False
                    |> Expect.equal False
        ]


main : Program Never
main =
    run emit tests


port emit : ( String, Value ) -> Cmd msg
```

 - All the tests for xElm exercises can be run from the top level of the repo with `bin/build.sh`. Please run this command before submitting your PR.

 - If you are submitting a new exercise, be sure to add it to the appropriate place in the `config.json` and `elm-package.json` files. Also, please run `bin/fetch-configlet && bin/configlet` to ensure the exercise is configured correctly.

## License

The MIT License (MIT)

Copyright (c) 2016 Katrina Owen, _@kytrinyx.com