chain compare operator.scala

object Example {
        
  implicit class NumberEx[A](val left:A)(implicit num:Numeric[A]) {
    def <== (right:A) = (num.lteq(left, right), right)
    def >== (right:A) = (num.gteq(left, right), right)
  }
  implicit class BoolNumberEx[A](val temp:(Boolean, A))(implicit num:Numeric[A]) {
    def <== (right:A) = (temp._1 & num.lteq(temp._2, right), right)
    def >== (right:A) = (temp._1 & num.gteq(temp._2, right), right)
  }
  implicit def boolNumberToBool[A](temp:(Boolean, A)) = temp._1

  def main(args: Array[String]) {
    val x = 15
    if(10 <== x <== 20) println(1)
    if(20 <== x <== 10) println(2)
    if(30 >== x*2 >== 20 >== x) println(3)
    if(15 >== x <== 15) println(4)
  }
  // result:
  // 1
  // 3
  // 4
}