Scala Tutorial - Scala Functions

Scala has both functions and methods.

A Scala method is a part of a class that has a name and a signature. A function in Scala is a complete object that can be assigned to a variable.

A function definition can appear anywhere in a source file.

Function without Parameter

To define a function in Scala, use the def keyword followed by the method name and the method body as shown as follows.

def hello() = {"Hello World!"}

The equal sign = is used as a separator between the method signature and the method body.

We can invoke this function using either hello() or hello.

object Main {
  def main(args: Array[String]) {
      def hello() = {"Hello World!"} 
      println(hello );
  }
}

We can also include the optional return type as shown as follows.

def hello():String = {"Hello World!"}

We can remove the parentheses from the method body altogether.

def hello() = "Hello World!"

We can also remove the parentheses from the method signature altogether.

def hello = "Hello World!"

The following code shows how to create a function with parameters.

def square (i:Int) = {i*i}

The body of the functions are expressions, 
where the final line becomes the return value of the function.

We can invoke this function as square(2).

object Main {
  def main(args: Array[String]) {
      def square (i:Int) = {i*i} 
      println(square(2) );
  }
}

We can provide multiple parameters in a function. Multiple parameters are separated by commas as illustrated in the following example.

def add(x: Int, y: Int): Int = { x + y }

We can now invoke this function by passing actual parameters to the add function.

object Main {
  def main(args: Array[String]) {
      def add(x: Int, y: Int): Int = { x + y } 
      
      println(add(5, 5) );
  }
}