     # The method `plus` creates a new Delaunay triangulation with the given
     # `Point2d` instance added as a site.
     plus: (p) ->
-      # We return the current instance unchanged if the site is already in.
       if @sites__.contains p
         this
-      # Otherwise, there's work to do...
       else
         # ...
 

    # triangle in this triangulation, if any, which contains the two or three
    # given vertices in the correct order.
    find: (a, b, c) ->
      # If three vertices are given, we look for all three possible vertex
      # orders with the same orientation in the triangle list.  Otherwise, we
      # look for the corresponding third vertex, if any, and call find
      # recursively.
     if c?
        seq(seq(a, b, c), seq(b, c, a), seq(c, a, b)).
          find((t) => @triangles__.contains(t))

# The function `circumCircleCenter` computes the center of the circum-circle
# of a given triangle, specified by three input points.
circumCircleCenter = (a, b, c) ->
  n = liftedNormal a, b, c
  unlift n.times -0.5 / n.z if Math.abs(n.z) > 1e-6

