SKB – Scala Stream


This article is part of the Scala knowledge bits Series.

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 Stream.

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 Stream !

An other data structure today ! After seeing List, Set. Let’s talk about Stream, now called LazyList in Scala 2.13+.

This is a bit of a longer exercise because there are several ways to create a LazyList and several ways to use it. Remember, this is your journey. If you only have the time to complete the beginning, you can move on or come back to it later.

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


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.

But if you get stuck, scroll down to get more information.

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 (HXLsbXJQSVSKmS333hXm6w).

More information about Scala Stream

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

In the first section, you saw how to create a LazyList recursively using the symbol #::. You also learned that you can take as many elements as you want, but since Scala values immutability, doing it several times in a row will always returns the same elements. Make sure to read the log statements carefully.

In the second section, we are using LazyList.from to use the build-in tools that allow you to start a sequential stream starting at n and increasing one by one. You also see that map can be used to modify the outcome of the LazyList. And finally, take can only reduce the size of the stream.

In the third and final section, we are implementing factorial, once recursively and then using a LazyList. Have you notice the use of the foldLeft from previous SKB !?

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


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

Please ask questions or post feedback in the comments below.

Feel free to try on the next Scala Knowledege Bit.

If you are curious about the previous Scala knowledge Bits, go check it out! 🙂

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