DZone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
Please enter at least three characters to search
Refcards Trend Reports
Events Video Library
Refcards
Trend Reports

Events

View Events Video Library

Zones

Culture and Methodologies Agile Career Development Methodologies Team Management
Data Engineering AI/ML Big Data Data Databases IoT
Software Design and Architecture Cloud Architecture Containers Integration Microservices Performance Security
Coding Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Culture and Methodologies
Agile Career Development Methodologies Team Management
Data Engineering
AI/ML Big Data Data Databases IoT
Software Design and Architecture
Cloud Architecture Containers Integration Microservices Performance Security
Coding
Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance
Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks

Last call! Secure your stack and shape the future! Help dev teams across the globe navigate their software supply chain security challenges.

Modernize your data layer. Learn how to design cloud-native database architectures to meet the evolving demands of AI and GenAI workloads.

Releasing software shouldn't be stressful or risky. Learn how to leverage progressive delivery techniques to ensure safer deployments.

Avoid machine learning mistakes and boost model performance! Discover key ML patterns, anti-patterns, data strategies, and more.

Related

  • Mastering Advanced Aggregations in Spark SQL
  • Thermometer Continuation in Scala
  • Deploying a Scala Play Application to Heroku: A Step-by-Step Guide
  • Exploring Operator, OpenAI’s New AI Agent

Trending

  • Agile and Quality Engineering: A Holistic Perspective
  • Apache Doris vs Elasticsearch: An In-Depth Comparative Analysis
  • A Guide to Developing Large Language Models Part 1: Pretraining
  • Breaking Bottlenecks: Applying the Theory of Constraints to Software Development
  1. DZone
  2. Coding
  3. Languages
  4. "Operator Overloading" in Scala

"Operator Overloading" in Scala

By 
Tom Jefferys user avatar
Tom Jefferys
·
Apr. 27, 12 · Interview
Likes (1)
Comment
Save
Tweet
Share
40.9K Views

Join the DZone community and get the full member experience.

Join For Free

So, I've been teaching myself Scala recently, and it's a very interesting language.

One of the nice things I like about it, is it's support for creating DSLs, domain specific languages. A domain specific language - or at least my understanding of it - is a language that is written specifically for one problem domain. One example would be SQL, great for querying relational databases, useless for creating first person shooters.

Of course Scala itself is not a DSL, it's a general purpose language. However it does offer several features that allow you to simulate a DSL, in particular operator overloading, and implicit conversions. In this post I'm going to focus on the first of these...

Operator Overloading

So what's operator overloading?

Well operators are typically things such as +, -, and !. You know those things you use to do arithmetic on numbers, or occasionally for manipulating Strings. Well, operator overloading - just like method overloading - allows you to redefine their behaviour for a particular type, and give them meaning for your own custom classes.

Hang on a minute! I'm sure someone once told me operator overloading was evil?

Indeed, this is quite a controversial topic. It's considered far too open for abuse by some, and was so maligned in C++ that the creators of Java deliberately disallowed it (excepting "+" for String concatenation).

I'm of a slightly different opinion, used responsibly it can be very useful. For example lots of different objects support a concept of addition, so why not just use an addition operator?

Lets say you were developing a complex number class, and you want to support addition. Wouldn't it be nicer to write...

Complex result = complex1 + complex2;

...rather than...

Complex result = complex1.add(complex2);

The first example is much more natural don't you think?

So Scala allows you to overload operators then?

Well, not really. In fact, technically not at all.

So all this is just a tease? This is the most stupid blog post I've ever read. Scala's rubbish. I'm going back to Algol 68.

Wait a second, I've not finished. You see Scala doesn't support operator overloading, because it doesn't have operators!

Scala doesn't have operators? You've gone mad, I write stuff like "sum = 2 + 3" all the time, and what about all those funny list operations? "::", and ":/". They look like operators to me!

Well they're not. The thing is, Scala has a rather relaxed attitude to what you can name a method.

When you write...

sum = 2 + 3,

...you're actually calling a method called + on a RichInt type with a value of 2. You could even rewrite it as...

sum = 2.+(3)

...if you really really wanted to.

Aha, I got it. So how do you go about overloading an operator then?

Simple, it's exactly the same as writing a normal method. Here's an example.

class Complex(val real : Double, val imag : Double) {
   
  def +(that: Complex) =
            new Complex(this.real + that.real, this.imag + that.imag)
   
  def -(that: Complex) =
            new Complex(this.real - that.real, this.imag - that.imag)
 
  override def toString = real + " + " + imag + "i"
   
}
 
object Complex {
  def main(args : Array[String]) : Unit = {
       var a = new Complex(4.0,5.0)
       var b = new Complex(2.0,3.0)
       println(a)  // 4.0 + 5.0i
       println(a + b)  // 6.0 + 8.0i
       println(a - b)  // 2.0 + 2.0i
  }
}

Ok that's nice, what if I wanted a "not" operator though, ie something like a "!"

That's a unary prefix operator, and yes scala can support these, although in a more limited fashion than an infix operator like "+"

Only four operators can be supported in this fashion, +, -, !, and ~. You simply need to call your methods unary_! or unary_~, etc. Here's how you might add a "~" to calculate the magnitude of a Complex number to our complex number class

class Complex(val real : Double, val imag : Double) {
    // ...
    def unary_~ = Math.sqrt(real * real + imag * imag)
}
 
object Complex {
  def main(args : Array[String]) : Unit = {
     var b = new Complex(2.0,3.0)
     prinln(~b) //  3.60555
   }
}

So that's all pretty simple, but please use responsibly. Don't create methods called "+" unless your class really does something that could be interpreted as addition. And never ever redefine the binary shift left operator "<<" as some sort of substitute for println. It's not clever and you'll make the Scala gods angry.

Hope you found that useful. Next up I'll cover implicit conversions. Another nice feature of Scala that really allows you to write your code in a more natural way

 

 

Operator (extension) Scala (programming language)

Published at DZone with permission of Tom Jefferys, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Related

  • Mastering Advanced Aggregations in Spark SQL
  • Thermometer Continuation in Scala
  • Deploying a Scala Play Application to Heroku: A Step-by-Step Guide
  • Exploring Operator, OpenAI’s New AI Agent

Partner Resources

×

Comments
Oops! Something Went Wrong

The likes didn't load as expected. Please refresh the page and try again.

ABOUT US

  • About DZone
  • Support and feedback
  • Community research
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • Become a Contributor
  • Core Program
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 3343 Perimeter Hill Drive
  • Suite 100
  • Nashville, TN 37211
  • support@dzone.com

Let's be friends:

Likes
There are no likes...yet! 👀
Be the first to like this post!
It looks like you're not logged in.
Sign in to see who liked this post!