anchor.diff:  
   ;;------------------------------------------------------------
   
  -(defun %init-data (body)
  -  (setf (%geometry-user-data body) (make-pointer (%add-geom-to-system body)))
  -  body)
  -
  -(defun make-null-geometry (world)
  +(defn-inline %init-data ((geometry geometry)) geometry
  +  (declare (optimize (speed 3) (safety 0) (debug 0)))
  +  (setf (%geometry-user-data geometry)
  +        (make-pointer (%add-geom-to-system geometry)))
  +  geometry)
  +
  +(defn make-null-geometry ((world world)) null-geometry
     "Create a transparent collision primitive. Some times the
      application needs to create helper rigid bodies that will never
      collide with other bodies, for example the neck of a rag doll, or an
  
positive.code:   (declare (ignore wptr mesh tolerance m4))
    (error "Not implemented"))
  
  (defun %make-convex-hull-from-points (wptr points tolerance m4)
    (assert (>= (length points) 4))
    (let ((len (length points)))
      (with-foreign-object (p-ptr :float (* 3 len))
  
negative.code:         :ptr (newtoncreatecapsule
                wptr (float radius-0) (float radius-1) (float height) 0 m4))))))
  
  (defn make-cylinder-geometry ((world world)
                                &key
                                (radius-0 single-float 1f0)
                                (radius-1 single-float 1f0)
                                (height single-float 4f0)
                                (offset-matrix4 (simple-array single-float (16)) (m4:identity)))
      cylinder-geometry
    "Create a cylinder primitive for collision."
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (let ((wptr (%world-ptr world)))
      (with-foreign-array (m4 offset-matrix4 '(:array :float 16))
        (%init-data
  