Scala 实数区间、整数区间

Question

如何定义这两个简单的 Interval 类的样板消除超类？

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)
}

我试过了

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)
}

但是 min 和 max 没有在 union 方法中编译（因为 Number[T] 没有 min/max）。

您能否提供一个优雅的超类，以一种简洁的、一次且仅一次的样板代码避免方式处理 mid 和 union 方法？

Answer 1

我认为您正在寻找 scala.math.Numeric 类型类：

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)
}