1

I have two implicit declarations that "redefine" x as an operator:

import scala.io.StdIn._
import util._
import scala.language.postfixOps


case class Rectangle(width: Int, height: Int)
case class Circle(ratio: Integer)
case class Cylinder[T](ratio: T, height: T)


object implicitsExample1 {

    implicit class RectangleMaker(width: Int) {
        def x(height: Int) = Rectangle(width, height)
    }

    implicit class CircleMaker(ratio: Int) {
        def c = Circle(ratio)
    }

    implicit class CylinderMaker[T](ratio: T) {
        def x(height: T) = Cylinder(ratio, height)
    }


    def main(args: Array[String]) {

        val myRectangle = 3 x 4
        val myCircle = 3 c
        val myCylinder = 4 x 5

        println("myRectangle = " + myRectangle)

        println("myCircle = " + myCircle) 

        println("myCylinder = " + myCylinder)

    }

}

Here my output gives:

myRectangle = Rectangle(3,4)
myCircle = Circle(3)
myCylinder = Rectangle(4,5)

What I need to do to have something like: 

myCylinder = Cylinder[Int](4,5)

I understand that the chosen implicit conversion is the first one declared but is there a way to specify the use of the Cylinder one?

Mario Galic
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Jose Cabrera Zuniga
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  • The chosen implicit conversion is not the first one declared, but the one that has the most specific parameter types. At least you could do `new CylinderMaker(4) x 5`, but it's not a pretty solution. – Bubletan Jun 26 '19 at 23:08

1 Answers1

4

Try combining RectangleMaker and CylinderMaker into a single ShapeMaker implicit class like so

implicit class ShapeMaker[T](width: T) {
  def x(height: T)(implicit ev: T =:= Int) = Rectangle(width, height)
  def x(height: T) = Cylinder[T](width, height)
}

and provide type ascriptions to value definitions like so

val myRectangle: Rectangle = 3 x 4
val myCircle = 3 c
val myCylinder: Cylinder[Int] = 4 x 5

which outputs

myRectangle = Rectangle(3,4)
myCircle = Circle(3)
myCylinder = Cylinder(4,5)
Mario Galic
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