A functional, rules-based Fizzbuzz in Scala

functional_fizzbuzz.sc

// functional, rules-based fizzbuzz
// inspired heavily by http://boston.conman.org/2020/06/08.1
def fizzbuzz(num: Int): String = {
  def ifElse(matchNum: Int, ifMatch: String, otherwise: String => String): String => String = {
    if (num % matchNum == 0) {
      _ => ifMatch + otherwise("")
    } else {
      otherwise
    }
  }

  def fizz(otherwise: String => String) = ifElse(3, "Fizz", otherwise)
  def buzz(otherwise: String => String) = ifElse(5, "Buzz", otherwise)

  //fizz(buzz(identity))(num.toString)

  // rules always seem to change
  val rules = List(
    fizz(_),
    buzz(_)
  )
  // composing the rules makes the world flexible
  val engine = rules.reduce(_.compose(_))(identity)
  engine(num.toString)
}

1.to(100).foreach(n => println(s"$n: ${fizzbuzz(n)}"))