SKB – Scala infix notation


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 infix notation.

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 infix notation !

This SKB will teach you a little more about some syntax allowed by the Scala language: infix.

It allows you to remove the . and the () when using a method.

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 (5YZMNrc1R5WjgZlBc772Kw).

More information about Scala infix notation

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

First of all, did you realize that every operation that seems to be “magic” like the + or == are just function like any other. But by habit , we use the infix notation for those by default. It is possible to use the “normal” notation with the . and the () but let’s be honest, it looks weird !

You can use the infix notation for every method that takes one argument. Which means you can use it for map, flatMap and all the other ones.

We also kind of saw it quickly previously when we talked about reduce. We saw that we could turn

list.reduce ( (a, b) => a.combineWith(b) )
list.reduce ( _ combinedWith _ )
You now understand one part of puzzle. The second part being the _ that we are going to see soon.

One last note, be careful not to abuse it or the code can become extremely horrible to decipher. You could chain methods are methods and lost track of which value is executing what.

a map _ combined v map _ + 1
This example is hard to read. Does combined return a list ? What is the second map applied to ? So, be careful !

It is also possible to use infix notation for function that has no arguments, but it is an extra feature, not included by default that you need to enable. To learn more, you can search for scala.language.postfixOps which allow you to use infix notation even without an argument.

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


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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