anchor.diff:  (in-package :cl-user)
   (defpackage cl-cuda-interop-examples.nbody
     (:use :cl
  -        :cl-cuda)
  -  (:export :main
  -           :*gpu*))
  +        :cl-cuda
  +        :cl-cuda-interop)
  +  (:export :main))
   (in-package :cl-cuda-interop-examples.nbody)
   
   
  
positive.code:         (window (make-instance 'nbody-window)))
      (glut:display-window window) ; GLUT window must be created before initializing nbody-demo
      (with-nbody-demo (demo 2048 :gpu gpu :interop interop)
        (with-frame-rate-counter (counter)
          (setf (slot-value window 'nbody-demo) demo
                (slot-value window 'counter)    counter)
          (glut:main-loop)))))
  
  
  (defun not-implemented ()
    (error "not implemented."))
  
negative.code: 
  (defun release-particle-renderer (renderer)
    (destroy-texture renderer)
    (release-shader renderer))
  
  (defun release-shader (renderer)
    (declare (ignorable renderer))
    (values))
  
  (defun destroy-texture (renderer)
    (cffi:foreign-free (particle-renderer-texture-data renderer)))
  
  (defun display-particle-renderer (renderer pos num-bodies mode)
    (let ((point-size  (particle-renderer-point-size  renderer))
          (sprite-size (particle-renderer-sprite-size renderer))
          (program     (particle-renderer-program     renderer))
          (texture     (particle-renderer-texture     renderer))
          (base-color  (particle-renderer-base-color  renderer)))
      (ecase mode
        (:particle-points
          (gl:color 1.0 1.0 1.0)
  