Scala Real Interval, Int Interval

boilerplate, scala, superclass

Solution

I think you are looking for the `scala.math.Numeric` typeclass:

class Interval[T] (val from: T, val to: T)(implicit num: Numeric[T]) { 
  import num.{mkNumericOps, mkOrderingOps}

  def mid: Double  = (from.toDouble + to.toDouble)/2.0 
  def union(other: Interval[T]) = new Interval(from min other.from, to max other.to)
}

Problem

How do I define a boiler-plate-eliminating superclass of these two simple Interval classes? ``` class IntInterval(val from: Int, val to: Int) { def mid: Double = (from+to)/2.0 def union(other: IntInterval) = IntInterval(from min other.from, to max other.to) } class DoubleInterval(val from: Double, val to: Double) { def mid: Double = (from+to)/2.0 def union(other: DoubleInterval) = DoubleInterval(from min other.from, to max other.to) } ``` I tried ``` class Interval[T <: Number[T]] (val from: T, val to: T) { def mid: Double = (from.doubleValue+to.doubleValue)/2.0 def union(other: IntInterval) = Interval(from min other.from, to max other.to) } ``` but the min and max did not compile in the union method (since Number[T] does not have min/max). Can you provide an elegant superclass which deals with both the mid and union methods in a neat, code-once-and-only-once boilerplate-avoiding way?

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