How to solve method delegation with scala implicits - scala

Question

How can i solve this simple problem. Class Conversion has a typed method from wich takes two type parameters A and B and returns a B from an A. I have defined some implicits in the companion object to provide default beahviour.
My Problem is when i try to forward the call to the Conversion class within another typed method which has the same signature it does not work. Here in my example i try to forward the call from function myFun to my Conversion class.
I got following error
not enough arguments for method from: (implicit f: A => B)
I am wondering why this makes any problems. Can someone explain me why and how to overcome this problem ?
Here is the code
object MyConversions {
implicit val IntToStr = (f:Int) => f.toString()
implicit val DoubleToStr = (f:Double) => f.toString()
implicit val BooleanToStr = (f:Boolean) => f.toString()
}
class Conversions{
def from[A,B](a:A)(implicit f:(A) => B) = {
f(a)
}
}
import MyConversions._;
def myFun[A,B](a:A){
// Error
new Conversions().from[A, B](a)
}
// Working
println( new Conversions().from[Int, String](3) )

Answer 1

The problem is that the Scala compiler cannot find an implicit value for the parameter f: (A) => B in the scope of myFun. What you have to do is to tell the compiler that myFun can only be called, when there is such a value available.
The following code should do the trick
object App {
trait Convertible[A, B] {
def convert(a: A): B
}
object Convertible {
implicit val int2String = new Convertible[Int, String] {
override def convert(a: Int): String = a.toString
}
implicit val float2String = new Convertible[Float, String] {
override def convert(a: Float): String = a.toString
}
}
def myFun[A ,B](a:A)(implicit converter: Convertible[A, B]): B = {
converter.convert(a)
}
def main(args: Array[String]): Unit = {
println(myFun(3))
}
}