Returning original collection type in generic method

Question

Say we want to make a function like minBy that returns all elements of equal minimalism in a collection:

def multiMinBy[A, B: Ordering](xs: Trav         


        

Answer 1

I think Miles Sabin solution is way too complex. Scala's collection already have the necessary machinery to make it work, with a very small change:

import scala.collection.TraversableLike
def multiMinBy[A, B: Ordering, C <: Traversable[A]]
              (xs: C with TraversableLike[A, C])
              (f: A => B): C = {
  val minVal = f(xs minBy f)
  xs filter (f(_) == minVal)
}