argmin and argmax

ArgMinMax.scala

object ArgMinMax {
  import scala.reflect.ClassTag

  def argmin[X: ClassTag, Y <% Ordered[Y] : ClassTag](n: Iterable[X], f: X => Y): X = {
    val (argmin: X, min: Y) = n.tail.fold((n.head, f(n.head))) { case ((a: X, m: Y), x: X) =>
      val fOfx: Y = f(x)
      if (fOfx < m) (x, fOfx) else (a, m)
    }
    return argmin
  }
  
  def argmax[X: ClassTag, Y <% Ordered[Y] : ClassTag](n: Iterable[X], f: X => Y): X = {
    val (argmin: X, min: Y) = n.tail.fold((n.head, f(n.head))) { case ((a: X, m: Y), x: X) =>
      val fOfx: Y = f(x)
      if (fOfx > m) (x, fOfx) else (a, m)
    }
    return argmin
  }
}