Geometric Vector collections

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A substantial amount of my code base uses 2 dimensional vectors. Pretty 
standard stuff, that hopefully will one day be included in the standard 
library:

final class Vec2 (val x: Double, val y: Double) extends PersistCompound
{
   override def equals(other: Any): Boolean = other match
   {
      case Vec2(px, py) => (x =\ px) && (y =\ py)
      case _ => false
   }
   def +(other: Vec2): Vec2 = Vec2(x + other.x, y + other.y)
...........
}

I'm currently using an implicit class to add methods:

object Vec2
{
   /** Translates each Vec2 member of collection equivalent to trav.map(_ + 
offset) */
      def +++ (offset: Vec2)(implicit bf: generic.CanBuildFrom[Repr, Vec2, 
Repr]): Repr =
      {
         def builder =
         { // extracted to keep method size under 35 bytes, so that it can 
be JIT-inlined
            val b = bf(travLike.repr)
            b.sizeHint(travLike)
            b
         }
         val b = builder
         for (x <- travLike) b += x + offset
         b.result
      } 

   /** Creates a bounding rectangle for a collection of 2d points */
      def boundingRect: BoundingRect =
      {
         var minX, maxX, minY, maxY = 0.0
         var i = 0
         for (v <- travLike)
         {
            if (i == 0)
            {
               minX = v.x
               maxX = v.x
               minY = v.y
               maxY = v.y
            }
            else
            {
               minX = minX.min(v.x)
               maxX = maxX.max(v.x)
               minY = minY.min(v.y)
               maxY = maxY.max(v.y)
            }
            i += 1
         }
         if (i == 0) throw new Exception("boundingRect method called on 
empty Vec2 collection") else {}
         BoundingRect(minX, maxX, minY, maxY)               
      }   
   ....................
   }
 } 

*1* Pretty horrible code. So my first question is: are those the correct 
ways to write those methods in 2.12 using the implicits if I want them to 
be efficient?

*2* Should there be an inline annotation on the + method of the Vec2 class?

*3* However I'm now wondering if I should use a custom collection class and 
then just create the methods directly on the class and always use the 
custom type where I currently have Seq[Vec2]. The two obvious 
implementation strategies are a wrapped Array or a custom List class with 
custom Cons and Nil classes. I'm leaning towards the latter as most of my 
Vec2 collections are small and it makes, building and iterating with 
immutability straight forward.

*4*  The 2d, 3d and 4d Vectors strike me as very important classes. The 3d 
Vector is given as the canonical example of a struct in Scala Native. So I 
wondered how the thinking for the new collections library in 2.13 will 
effect these classes?

*5* Will we be able to use Scala Native Vector Structs while still 
maintaining a largely common code base for ScalaJvm and ScalaJs? This seems 
to me completely entangled with the question of collections.

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