# SKB – Scala Either

## Introduction

Periodically, I will publish new exercises so you can slowly build up knowledge about Scala.

It is designed to be done in a very short amount of time and learn a little bit each day, just to create a routine.

This episode will teach you about Scala `Either`.

Hope you are going to enjoy it! It is designed for anyone to learn Scala from scratch and slowly learn, one Bit at a time.

After this Bit, I would love to hear your feedback in the comments down below.

Feel free to join the Discord server as well if you would like some help and support from the rest of our community.

## What are we learning today?

Today we are going to learn about Scala `Either` !

`Either`, you will see, is kind of a in-between `Try` and `Option`.

Try to experiment to see the similarity and differences.

Time to try on the exercise on your own and scroll down for more information when you are done or if you are stuck.

## Exercise

Here is an exercise to complete today.

If I did my job well, you should be able to guess by yourself the solution based on what you previously learned and based on the clues.

The goal of the exercise is to replace the `???` by a piece of code so that the exercise compiles and that’s how you win! Good luck!

You can fill the exercise right in here:

Or, if it does not load, go on to Scastie (bzjEzMzhQmSOiJm2bejFkw).

## More information about Scala `Either`

In this exercise you will learn (or have learned, if you have already solved the puzzle) about Scala `Either`.

Similar to `Option`, you can create `Either` in two ways:

• `Right` which would be similar to `Some`
• `Left` which, over time, became similar to `None`, except you can store information. I am saying “over time” because up until Scala v2.12+, `Either` was not Right-bias. `Left` and `Right` were just two Types. But now, `Left` is accepting to carry error messages and `Right` to be the channel for successes.

You can test which Type is `Either` using `isLeft` and `isRight`. You can also use `map`, `flatMap`, etc… once again. You must be starting to know those functions pretty well by now. This is where the Right-bias come into play. `map` will take a function that modify the type contained in `Right` and will not do anything if the `Either` contains a `Left`.

If you would like to specifically act on `Left` or `Right`, you can use the `.left` and `.right` methods to project the `Either` on one side of the other. For instance, to modify the content of the `Left` when it is there, you can do `.left.map(...)`.

One major difference with `Try` is that `Either` will not catch the Exception. If an exception is thrown inside an `Either` it will propagate. Inside a `Try` it will be captured inside the `Failure` channel.

Feel free to go back to the exercise, modify the code to try out new things and get a better intuition for Scala `Either`.

## Conclusion

I hope you have learned something new or had fun during this Scala Knowledge Bit.