Oh ... it does "print money"

gistfile1.scala

sealed trait Function3D {
	def apply(vec: Vector3): Float

	override def toString = getClass.getSimpleName + ":" + parameterString


	def encodeXML: Elem

	/**
	 * Cheap trick to enforce toString
	 */
	def parameterString: String
}

trait AggregateFunction3D extends Function3D {
	var children: List[Function3D]

	override def encodeXML: Elem =
		<function type={getClass.getName} parameters={parameterString}>
			<children>
				{children.map(_.encodeXML)}
			</children>
		</function>

}

trait LeafFunction3D extends Function3D {

	override def encodeXML: Elem =
			<function type={getClass.getName} parameters={parameterString}/>
}

trait ModifierFunction3D extends Function3D {
	var input: Function3D = null

	override def encodeXML: Elem =
		<function type={getClass.getName} parameters={parameterString}>
			<input>
				{input.encodeXML}
			</input>
		</function>
}