Scala example source code file (t0786.scala)

This example Scala source code file (t0786.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

array, implicitproblem, int, int, m, m, rep, rep, t, t

The Scala t0786.scala source code

object ImplicitProblem {
  class M[T]

  def nullval[T] = null.asInstanceOf[T];
    
  trait Rep[T] {
    def eval: Int
  }
    
  implicit def toRep0(n: Int) = new Rep[Int] {
    def eval = 0
  }
    
  implicit def toRepN[T](n: M[T])(implicit f: T => Rep[T]) = new Rep[M[T]] {
    def eval = f(nullval[T]).eval + 1
  }

  def depth[T <% Rep[T]](n: T) = n.eval

  def main(args: Array[String]) {
    println(depth(nullval[M[Int]]))  // (1) this works   
    println(nullval[M[Int]].eval)    // (2) this works
      
    type m = M[Int]
    println(depth(nullval[m]))     // (3) this doesn't compile on 2.7.RC1    
    println(nullval[m].eval)       // (4) this works
  }

}