NoImports.scala

/**
 * This is an exmaple of how to program in scala without the use of imports or
 * global namespaces. Foo seeing Bar's members does not rely on the fact
 * that they are in the same package.
 *
 * Inspired by Gilad Bracha's talk at the Emerging Languages conference in 2010.
 *
 * Built with scala 2.8.0-final
 */

class Foo(val bar: Bar) {
  private class FooFrob extends bar.Frob {
    override def apply() = 1
  }

  class FrobMaker extends bar.FrobMaker {
    def apply(): bar.Frob = new FooFrob
  }
}


trait Bar {
  trait Frob {
    def apply() = 0
  }

  trait FrobMaker {
    def apply(): Frob;
  }
}

object Main {
  def main(args: Array[String]) {
    // Passing in an anonymous subclass of the Bar trait.
    val foo = new Foo(new Bar{})
    // This calls the apply method on Foo.FrobMaker to get a Bar.FrobMaker
    // and then calls apply on Bar.FrobMaker to construct a Frob.
    val frob = new foo.FrobMaker()()
    println("frob() = " + frob())
  }
}

Of course, the whole point of no global namespace is that you can avoid details like Array[String] referring to global names.