SKB – Scala Call-by-name Parameters


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 ‘call-by-name’ parameters.

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 ‘call-by-name’ parameters !

There are two ways to give parameters to a function in most programming languages: ‘by-value’ and ‘call-by-name’.

The ‘by-value’ way is what we have seen in previous SKBs when we used functions and methods.

In this SKB, focus your attention on the way the parameters of the function are being declared and the syntax, notice anything?

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 (XkgpvxRaQdSnfdO2yWuSOg).

More information about Scala ‘call-by-name’ parameters

In this exercise you will learn (or have learned, if you have already solved the puzzle) about Scala ‘call-by-name’ parameters.

Did you notice the => Int in the parameter list?

You can understand it as if it was () => Int, meaning a function that will return Int when called.

The content of the parameter will not be evaluated until needed. Be aware that it will be re-evaluated for each time it is called. But we will look into it into a more advanced SKB later on.

Feel free to go back to the exercise, modify the code to try out new things and get a better intuition for Scala ‘call-by-name’ parameters.


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! 🙂

2 thoughts on “SKB – Scala Call-by-name Parameters”

  1. I really think that using many parentheses pairs on method signature (called Currying – I googled it) makes this exercise a lot more confusing than it should. I get the idea of calling by name but concept of currying it not clear yet and it’s not necessary for this topic.


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