anchor.diff:    (when (eq (glop:keysym event) :escape)
       (glop:push-close-event window)))
   
  -(defun link-program ()
  +(defun link-program (shader-source fragment-source)
     (let ((vs (gl:create-shader :vertex-shader))
   	(fs (gl:create-shader :fragment-shader))
   	(pg (gl:create-program)))
  -    (gl:shader-source vs *shader-source*)
  +    (gl:shader-source vs shader-source)
       (gl:compile-shader vs)
       ;;(print (gl:get-shader-info-log vs))
  -    (gl:shader-source fs *fragment-source*)
  +    (gl:shader-source fs fragment-source)
       (gl:compile-shader fs)
       ;;(print (gl:get-shader-info-log fs))
       (gl:attach-shader pg vs)
  
positive.code: (require 'cl-opengl) 
  (require 'glop)
  
  (defvar *shader-source* 
  "#version 330 core
  layout(location = 0) in vec3 in_Position;
  void main() {
  
negative.code:   gl_Position.w = 1.0;
  }")
  
  (defparameter *fragment-source*
  "#version 330 core
  out vec3 out_Color;
  void main() {
  