Scala monoid range

range_monoid.scala

object MonoidRange {

  case class MonoidRangeBuilder[T](from: T, to: T, incl: Boolean)(implicit mo: Monoid[T], ordering: Ordering[T]) {
    def by(step: T) = Stream.iterate(from) { previous: T =>
      previous + step
    }.takeWhile { x =>
      if (incl) {
        ordering.lteq(x, to)
      } else {
        ordering.lt(x, to)
      }
    }
  }

  implicit class RichMonoidRange[T](wrap: T)(implicit mo: Monoid[T], ordering: Ordering[T]) {

    def until(incl: T) = MonoidRangeBuilder(wrap, incl, false)

    def to(incl: T) = MonoidRangeBuilder(wrap, incl, true)

  }
}

until: IndexedSeq[com.twitter.util.Duration] = 
   Vector(10.seconds, 12.seconds, 14.seconds, 16.seconds, 18.seconds)

to: IndexedSeq[com.twitter.util.Duration] = 
   Vector(10.seconds, 12.seconds, 14.seconds, 16.seconds, 18.seconds, 20.seconds)


import MonoidRange._
import com.twitter.util.Duration
import java.util.concurrent.TimeUnit

implicit val durationMondoid = new Monoid[Duration] {
  override def zero: Duration = Duration(0, TimeUnit.SECONDS)

  override def plus(l: Duration, r: Duration): Duration = {
    l + r
  }
}


import com.twitter.conversions.time._

val until = 10.seconds until 20.seconds by 2.seconds toIndexedSeq
val to = 10.seconds to 20.seconds by 2.seconds toIndexedSeq