Scala使用隐式转换进行比较

 Boy.scala

class Boy(val name: String, val faceValue: Int) extends Comparable[Boy]{
  override def compareTo(o: Boy): Int = {
    this.faceValue - o.faceValue
  }
}

 Girl.scala

class Girl(val name: String, val faceValue: Int, val size: Int) {

}

  MissLeft.scala

//class MissLeft[T <% Ordered[T]] {
//
//  def choose(first: T, second: T) : T = {
//    if (first > second) first else second
//  }
//
//}

class MissLeft[T : Ordering] {

  def choose(first: T, second: T): T = {
    val ord = implicitly[Ordering[T]]
    if(ord.gt(first, second)) first else second
  }
}

object MissLeft {
  def main(args: Array[String]) {
    import MyPreDef.girlOrdering
    val ml = new MissLeft[Girl]
    val g1 = new Girl("hatanao", 98, 28)
    val g2 = new Girl("sora", 95, 33)
    val g = ml.choose(g1, g2)
    println(g.name)
  }
}

 MissRight.scala

class MissRight[T] {

  def choose(first: T, second: T)(implicit ord : T => Ordered[T]): T = {
    if(first > second) first else second
  }

  def select(first: T, second: T)(implicit ord : Ordering[T]): T ={
    if(ord.gt(first, second)) first else second
  }

  def random(first: T, second: T)(implicit ord : Ordering[T]): T ={
    import Ordered.orderingToOrdered
    if(first > second) first else second
  }

}

object MissRight {
  def main(args: Array[String]) {
    val mr = new MissRight[Girl]
    val g1 = new Girl("hatanao", 98, 28)
    val g2 = new Girl("sora", 95, 33)

    import MyPreDef.girlOrdering
    //val g = mr.choose(g1, g2)
    val g = mr.select(g1, g2)
    println(g.name)
  }
}

  MyPreDef.scala

object MyPreDef {

  implicit def girlToOrdered(girl: Girl) = new Ordered[Girl]{
    override def compare(that: Girl): Int = {
      if(girl.faceValue == that.faceValue) {
        girl.size - that.size
      } else {
        girl.faceValue - that.faceValue
      }
    }
  }

  implicit object girlOrdering extends Ordering[Girl] {
    override def compare(x: Girl, y: Girl): Int = {
      if(x.faceValue == y.faceValue) {
        x.size - y.size
      } else {
        x.faceValue - y.faceValue
      }
    }
  }
}

 MrRight.scala

class MrRight[T] {

  def choose[T <: Comparable[T]](first: T, second: T): T = {
    if(first.compareTo(second) > 0) first else second
  }

}

object MrRight {
  def main(args: Array[String]) {
    val mr = new MrRight[Boy]
    val b1 = new Boy("zhangsan", 99)
    val b2 = new Boy("lisi", 100)
    val b = mr.choose(b1, b2)
    println(b.name)
  }
}