Scala sort a set with ordering

Question

I am a beginner to Scala. I want to Sort a Set and then provide user with new sorted Set so old Set should remain the same.

I have already a trait like example BaseTrait[+A] and I want to enrich it.

trait BaseSet[+A] { //it extends scala Set

  def +[B >: A](item: B): BaseSet[B]

  def -[B >: A](item: B): BaseSet[B]

  def size: Int

  def contains[B >: A](item: B): Boolean  

}

trait SetWithSort[+A] extends BaseSet[A] {

  abstract def sort[B](implicit ordering: Ordering[_ >: B]): Set[B]

  def logicBeforeSorting(): Set[B] ={
    sort
  }
}

object MainObject {
  def OrderByName:Ordering[String] => Set[String] = ???  

  def execute[T](callback:Ordering[T]): Ordering[T] = callback //Problem, I // want Set[T] here

// I want to get a new Set with elements sorted as per my provided ordering 

}

Answer 1

You can use SortedSet as mentioned in the comments, example:

import scala.collection.SortedSet

def sortSet[A](unsortedSet: Set[A])(implicit ordering: Ordering[A]): SortedSet[A] = 
    SortedSet.empty[A] ++ unsortedSet

If you provide an implicit argument of type Ordering[A], this ordering will be used.

Usage with default ordering:

sortSet(Set(2, -1, 0, -2, 1)) // result TreeSet(-2, -1, 0, 1, 2)

the above works because Scala already provides an implicit Ordering[Int] in scope

Usage with provided ordering:

implicit val reverseOrdering = Ordering[Int].reverse
sortSet(Set(-15, 100, -3, 101, -5)) // result TreeSet(101, 100, -3, -5, -15)

// or by providing ordering directly:
val reverseOrdering = Ordering[Int].reverse
sortSet(Set(-15, 100, -3, 101, -5))(reverseOrdering) // result TreeSet(101, 100, -3, -5, -15)