Yet another FizzBuzz implementation...

Program.scala

// After reading the trials and tribulations here 
// http://www.learningclojure.com/2014/05/fizz-buzz-interview-question.html?utm_source=dlvr.it&utm_medium=twitter
// I decided to see how easy this is using sum types.
// Answer: Pretty easy. :D

sealed trait \/[+L, +R]
case class \[L](l: L) extends \/[L, Nothing]
case class /[R](r: R) extends \/[Nothing, R]

object Program {
  def numbers(n: Int): Stream[Int] = Stream.cons(n, numbers(n + 1))
  
  def transformIf[L,R](e: \/[L, R])(p: L => Boolean)(f: L => R): \/[L, R] = e match {
    case \(l) => if(p(l)) /(f(l)) else \(l)
    case /(r) => /(r)
  }
  
  def main(args: Array[String]): Unit = {
	numbers(1).take(100)
	  .map(\(_))
	  .map(transformIf(_)(_ % 15 == 0)(_ => "fizzbuzz"))
	  .map(transformIf(_)(_ % 5 == 0)(_ => "buzz"))
	  .map(transformIf(_)(_ % 3 == 0)(_ => "fizz")).toList.foreach(println)
  }
}