anchor.diff:          *array* (make-gpu-array (list (list (v!  0.5 -0.36 0) (v! 0 1 0 1))
                                         (list (v!    0   0.5 0) (v! 1 0 0 1))
                                         (list (v! -0.5 -0.36 0) (v! 0 0 1 1)))
  -                                :element-type 'pos-col)
  +                                :element-type 'g-pc)
      *stream* (make-buffer-stream *array*))
     (loop :while *running* :do (continuable (step-demo))))
   
  
positive.code:   (evt:pump-events)
    (update-swank)
    (gl:clear :color-buffer-bit)
    (gmap #'prog-1 *stream*)
    (cgl:update-display))
  
  (defun run-demo ()
  
negative.code: (defparameter *stream* nil)
  (defparameter *running* nil)
  
  (defstruct-g test ()
    (scale :float :accessor scale))
  
  (defun-g vert ((vert g-pc) &uniform (hmm test :ubo))
    (values (v! (* (pos vert) (scale hmm)) 1.0)
            (:smooth (col vert))))
  
  