gistfile1.java

(env-2.6)MacBook:dynamic_scala nicolas $ cat DynamoDemo.scala
// This is a class in some library
class ExternalClass(val a: Int, val b: String)

class InternalClass(val i: Int) {
    val j = i * 2
}

object DynamoDemo {
    def f(a: ExternalClass) = "" + a.a + " " + a.b
    def g(a: InternalClass) = (a.i + a.j) toString
    def h(a: {def x: Int; def y: String}) = "" + a.x + " " + a.y

    // Yeah yeah, showing off
    private def test(fun: => String): Unit = {
        println(fun)
    }

    def main(args: Array[String]): Unit = {
        val e = new ExternalClass(10, "Ten")
        val i = new InternalClass(20)

        // This looks normal
        test(f(e))
        test(g(i))

        // Magic starts here
        test(h(new {val x = 30; val y = "thirty"}))
        test(f(i))
        test(g(e))
        test(h(e))
    }

    implicit def extToInt(o: ExternalClass): InternalClass = {
        new InternalClass(o.a)
    }

    implicit def intToExt(o: InternalClass): ExternalClass = {
        new ExternalClass(o.j, o.i toString)
    }

    implicit def extToFCompatible(o: ExternalClass): 
        {def x: Int; def y: String} = {
        new {val x = o.a; val y = o.b}
    }
}
// vim: set ts=4 sw=4 et:
(env-2.6)MacBook:dynamic_scala nicolas $ scalac DynamoDemo.scala
(env-2.6)MacBook:dynamic_scala nicolas $ scala DynamoDemo
10 Ten
60
30 thirty
40 20
30
10 Ten