What's the best way to inverse sort in scala?

Question

What is the best way to do an inverse sort in scala? I imagine the following is somewhat slow.

list.sortBy(_.size).reverse

Is there a conv

Answer 1

sortBy has implicit parameter ord which provides ordering

def sortBy [B] (f: (A) ⇒ B)(implicit ord: Ordering[B]): List[A]

so, we can define own Ordering object

scala> implicit object Comp extends Ordering[Int] {
 | override def compare (x: Int, y: Int): Int = y - x
 | }
defined module Comp

List(3,2,5,1,6).sortBy(x => x)
res5: List[Int] = List(6, 5, 3, 2, 1)