Macro for generating Quantities

[gbeaty]

Apple, Orange and Pear types could be generated, with no chance of mis-ordering:

trait AppleOrange extends Quantities {
  type Apple = dimOf[_0]
  type Orange = dimOf[p1]
}
object AppleOrange extends AppleOrange {
  type quants = Apple.type :: Orange.type :: QNil
}
object Pear extends BaseQuantity
object AppleOrangePear extends AppleOrange {
  override type quants = AppleOrange.quants#append[Pear.type :: QNil]
  type Pear = dimOf[p2]
}