Scala Design Patterns - Second Edition

Function literals

Let's have a look at an example:

class FunctionLiterals {  val sum = (a: Int, b: Int) => a + b}object FunctionLiterals {  def main(args: Array[String]): Unit = {    val obj = new FunctionLiterals    System.out.println(s"3 + 9 = ${obj.sum(3, 9)}")  }}

Here, we can see how the sum field of the FunctionLiterals class is actually assigned a function. We can assign any function to a variable and then call it as if it was a function (essentially invoking its apply method). Functions can also be passed as parameters to other methods. Let's add the following to our FunctionLiterals class:

def runOperation(f: (Int, Int) => Int, a: Int, b: Int): Int = {  f(a, b)}

We can then pass the required function to runOperation, as follows:

obj.runOperation(obj.sum, ...