import scala.collection.{GenSeq, SeqLike}
import scala.math._
def minByFeature[A:Ordering,B](seq:GenSeq[B], feature:Function1[B,A]):B = {
  val featureseq = seq.map(feature)
  val minFeature = featureseq.min
  val minFeatureIndex = featureseq.indexOf(minFeature)
  seq(minFeatureIndex)
}

val l = List(-2,-3,-3,-4,-5)

minByFeature[Int,Int](l,(x=>abs(x)))