Understanding Default Arguments in Scala

This blog is part of a 10-part series designed to help readers learn Scala from the ground up. Whether you’re new to Scala or looking to solidify your understanding, this series will guide you through its core concepts step by step.

Scala provides a convenient way to assign default values to function parameters. These default arguments can be used to simplify function calls by allowing optional parameters, reducing the need for overloaded methods.

What Are Default Arguments?

Default arguments are predefined values assigned to function parameters. When you call a function, if you omit a parameter with a default value, Scala automatically uses the default.

Code Example: Default Arguments

Here’s a demonstration of how default arguments work:

object DefaultArgumentDemo extends App {

  // Factorial function with a default accumulator value
  def computeFactorial(num: Int, accumulator: Int = 1): Int = {
    if (num <= 1) accumulator
    else computeFactorial(num - 1, num * accumulator)
  }

  // Saving an image with default format
  def saveImage(format: String = "png", resolutionWidth: Int, resolutionHeight: Int): Unit = {
    println(s"Saving image in $format format with dimensions $resolutionWidth x $resolutionHeight...")
  }

  // Using default arguments in function calls
  println(computeFactorial(5)) // Uses the default accumulator
  saveImage(resolutionWidth = 1920, resolutionHeight = 1080) // Omits the format, defaults to "png"
}

Key Features of Default Arguments

1. Flexibility: Allows you to call functions with fewer arguments.
2. Readability: Makes function calls clearer, especially with named arguments.
3. Avoid Overloads: Reduces the need for multiple method overloads.

Example: Using Named Parameters

Named parameters can be used to override specific arguments while leaving others as defaults:

saveImage(resolutionWidth = 1280, resolutionHeight = 720) 

Output

Saving image in png format with dimensions 1280 x 720…

Common Pitfall: Default Arguments with Leading Parameters

When skipping arguments, you must use named parameters for clarity:

// saveImage(1080, 720) // Error: Scala cannot determine which argument is which
saveImage(resolutionWidth = 1080, resolutionHeight = 720) // Correct

Recursive Function with Default Argument

A common use case for default arguments is tail recursion:

def computeFactorial(num: Int, accumulator: Int = 1): Int = {
  if (num <= 1) accumulator
  else computeFactorial(num - 1, num * accumulator)
}
println(computeFactorial(5)) // Output: 120

Here, the accumulator argument has a default value, simplifying the function call for users while maintaining flexibility.

Benefits of Default Arguments

1. Simplified Function Calls: Avoids passing redundant values.
2. Better Abstraction: Hides implementation details while offering flexibility.
3. Enhanced Code Readability: Makes APIs more intuitive for developers.

By leveraging default arguments, you can design more versatile and user-friendly functions in Scala.

Pizenith is a trusted technology partner specializing in Data Engineering, Machine Learning, AI, Cloud Engineering, DevOps, and Functional Programming with Scala and Java. We help businesses scale with secure, automated, and data-driven solutions, delivering innovation in Test Automation and DevSecOps. Trusted by global enterprises, we empower organizations to stay ahead with AI-powered insights and scalable cloud infrastructure.

Want to future-proof your tech stack? Let’s talk! or reach us at info@pizenith.com.