Mastering Functional Programming

Introducing the flatMap function

Another example of a function that encapsulates a pattern of functional programming is flatMap. Imagine we need to create a function that computes the following mathematical expression: (2 / x) / y + 3. Let's try to do this with the division function that we defined previously:

def f2Match(x: Double, y: Double): Try[Double] =  divide(2, x) match {    case Success(r1) => divide(r1, y) match {      case Success(r2) => Success(r2 + 3)      case f@Failure(_) => f    }    case f@Failure(_) => f  }

The code becomes spaghetti-like here. First, we analyze the result of dividing 2 by x. If successful, we would divide it by y. Then we analyze the result of that division, and if there was no error, we add 3 to the result.

Here, we can no ...