enum class Planet(mass: Double, radius: Double) {
  private final val G = 6.67300E-11
  def surfaceGravity = G * mass / (radius * radius)
  def surfaceWeight(otherMass: Double) =  otherMass * surfaceGravity
}
object Planet {
  case MERCURY extends Planet(3.303e+23, 2.4397e6)
  case VENUS   extends Planet(4.869e+24, 6.0518e6)
  case EARTH   extends Planet(5.976e+24, 6.37814e6)
  case MARS    extends Planet(6.421e+23, 3.3972e6)
  case JUPITER extends Planet(1.9e+27,   7.1492e7)
  case SATURN  extends Planet(5.688e+26, 6.0268e7)
  case URANUS  extends Planet(8.686e+25, 2.5559e7)
  case NEPTUNE extends Planet(1.024e+26, 2.4746e7)
}
object Test {
  def main(args: Array[String]) = {
    import Planet._
    assert(enumValueNamed("SATURN") == SATURN)
    assert(enumValue(2) == EARTH)
    val earthWeight = 100
    val mass = earthWeight/EARTH.surfaceGravity
    for (p <- enumValues)
      println(s"Your weight on $p is ${p.surfaceWeight(mass)}")
  }
}