trait Philosophical {
    def philosphize() {
	println("I consume memory, therefore I am!")
    }
}

class Frog extends Philosphical {
 override def toString = "green"
}

class Animal
class Frog extends Animal with Philosophical {
    override def toString = "green"
}

class Rational(n: Int, d: Int) extends Ordered[Rational] {
    def compare(that: Rational) =
	(this.number * that.demon) - (that.number * this.denom)
}