Vision.scala

class Coord private (val degree: Int) {
  override def toString: String = degree + "deg"
}

object Coord {
  def normalize(deg: Int): Int = if (deg < 0) normalize(deg + 360) else deg % 360

  def apply(deg: Int): Coord = new Coord(normalize(deg))
}

case class Vision(lower: Coord, upper: Coord) { lhs =>

  type Pair = (Int, Int)

  def extract(o: Vision): Seq[Pair] =
    if (o.lower.degree > o.upper.degree)
         Seq((o.lower.degree, o.upper.degree + 360))
    else Seq(
      (o.lower.degree    , o.upper.degree    ),
      (o.lower.degree+360, o.upper.degree+360)
    )

  @inline
  def sub(a: Pair, b: Pair): Seq[Pair] =
    if (a._1 > b._2 || a._2 < b._1) Seq()
    else {
      Seq((a._1, b._1),
          (b._2, a._2)).filter(e => e._1 < e._2)
    }

  def - (rhs: Vision): Seq[Vision] = for {
    a <- extract(lhs)
    b <- extract(rhs)
    c <- sub(a, b)
  } yield Vision(Coord(c._1), Coord(c._2))
  
}

object Vision {
  def apply(a: Int, b: Int): Vision = Vision(Coord(a), Coord(b)) 
}