NumericRange.scala

abstract class NumericRange[T]
  (val start: T, val end: T, val step: T, val isInclusive: Boolean)
  (implicit num: Integral[T])
extends AbstractSeq[T] with IndexedSeq[T] with Serializable {

  final override def sum[B >: T](implicit num: Numeric[B]): B = {
    import num.Ops
    if (isEmpty) this.num fromInt 0
    else if (numRangeElements == 1) head
    else ((this.num fromInt numRangeElements) * (head + last) / (this.num fromInt 2))
  }

  ...
}