anchor.diff:    gl_Position.w = 1.0;
   }")
   
  -(defvar *fragment-source*
  +(defparameter *fragment-source*
   "#version 330 core
   out vec3 out_Color;
   void main() {
  
positive.code:     (let* ((vertex-array (gl:gen-vertex-array))
  	   (buffers (gl:gen-buffers 2))
  	   (vertex-buffer (elt buffers 0))
  	   (program (link-program)))
        (gl:bind-vertex-array vertex-array)
        (gl:bind-buffer :array-buffer vertex-buffer)
        (load-buffer-array #(-1.0 -1.0 0.0
  
negative.code: (require 'cl-opengl) 
  (require 'glop)
  
  (defparameter *shader-source* 
  "#version 330 core
  layout(location = 0) in vec3 in_Position;
  void main() {
  