Monoidal FizzBuzz In Scala by Dominic Fox

monoidal_fizzbuzz.scala

import scalaz._

object Main {

  case class FizzBuzz(elems: String*)

  implicit object FizzBuzzMonoid extends Monoid[FizzBuzz] {
    override def zero = FizzBuzz()
    override def append(f1: FizzBuzz, f2: => FizzBuzz): FizzBuzz = FizzBuzz(f1.elems ++ f2.elems :_*)
  }

  implicit object FuzzBuzzShow extends Show[FizzBuzz] {
    override def shows(f1: FizzBuzz): String = f1.elems.mkString("")
  }

  def interpreter(name: String, cond: Int => Boolean): Int => FizzBuzz = i =>
    if (cond(i)) FizzBuzz(name) else FizzBuzzMonoid.zero

  val fizz = interpreter("fizz", (i: Int) => (i % 3) == 0)
  val buzz = interpreter("buzz", (i: Int) => (i % 5) == 0)

  def fizzBuzzer[T](interpreters: (Int => T)*)(implicit m: Monoid[T], s: Show[T]): Int => String = i => {
    val interpreted: T = interpreters.map(_.apply(i)).fold(m.zero)(m.append(_, _))
    if (interpreted == m.zero) i.toString else s.shows(interpreted)
  }

  def main(args: Array[String]) {
    (1 to 100).map(fizzBuzzer(fizz, buzz)).foreach(println)
  }

}