     # 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
         # ...
 

# outside or on the circle through points a, b and c. A positive return value
# means inside, zero means on and a negative value means outside.
inclusionInCircumCircle = (a, b, c, d) ->

  # Equivalently, we can ask whether the lift of d is below, on or above the
  # plane formed by the lifts of the points a, b and c, which we can readily
  # read of the dot product of the lifted normal and the vector from the lift
  # of a to the lift of d.
  liftedNormal(a, b, c).dot lift(d).minus lift(a)



# 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

