Scala: Ordering contravariance

Question

Is there any reason why Scala\'s Ordering trait is not contravariant? A motivating example follows.

Suppose I want to perform an ordered insert. I may have

Answer 1

In the current API, these methods prevent it from being contravariant:

  /** Return `x` if `x` >= `y`, otherwise `y`. */
  def max(x: T, y: T): T = if (gteq(x, y)) x else y

  /** Return `x` if `x` <= `y`, otherwise `y`. */
  def min(x: T, y: T): T = if (lteq(x, y)) x else y