elm/exercises/strain/README.md

# Strain

Implement the `keep` and `discard` operation on collections. Given a collection
and a predicate on the collection's elements, `keep` returns a new collection
containing those elements where the predicate is true, while `discard` returns
a new collection containing those elements where the predicate is false.

For example, given the collection of numbers:

- 1, 2, 3, 4, 5

And the predicate:

- is the number even?

Then your keep operation should produce:

- 2, 4

While your discard operation should produce:

- 1, 3, 5

Note that the union of keep and discard is all the elements.

The functions may be called `keep` and `discard`, or they may need different
names in order to not clash with existing functions or concepts in your
language.

## Restrictions

Keep your hands off that filter/reject/whatchamacallit functionality
provided by your standard library!  Solve this one yourself using other
basic tools instead.

## Elm Installation

Refer to the [Exercism help page](http://exercism.io/languages/elm) for Elm
installation and learning resources.

## Writing the Code

The first time you start an exercise, you'll need to ensure you have the
appropriate dependencies installed.

```bash
$ npm install
```

Execute the tests with:

```bash
$ npm test
```

Automatically run tests again when you save changes:

```bash
$ npm run watch
```

As you work your way through the test suite, be sure to remove the `skip <|`
calls from each test until you get them all passing!

## Source

Conversation with James Edward Gray II [https://twitter.com/jeg2](https://twitter.com/jeg2)

## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.