anchor.diff:      (mapcar #'(lambda (shader) (gl:detach-shader program shader)) shaders)
       program))
   
  -(defun make-gl-array (vect)
  -  (let ((array (gl:alloc-gl-array :float (length vect))))
  +(defun make-gl-array (type vect)
  +  (let ((array (gl:alloc-gl-array type (length vect))))
       (dotimes (i (length vect))
         (setf (gl:glaref array i) (aref vect i)))
       array))
  
positive.code: 
  (in-package #:cl-foo)
  
  (defun read-shader (filename)
    (let ((shader (gl:create-shader (if (string= ".vert" (subseq filename (- (length filename) 5)))
                                        :vertex-shader
                                        :fragment-shader)))
          (pathname (merge-pathnames (asdf:system-source-directory :cl-foo) filename)))
      (gl:shader-source shader (alexandria:read-file-into-string pathname))
      (gl:compile-shader shader)
      (if (not (gl:get-shader shader :compile-status))
          (error (concatenate 'string "Error in " filename "~%" (gl:get-shader-info-log shader))))
  
negative.code:     (sdl2:with-window (window :title title :w width :h height :flags '(:shown :opengl))
        (sdl2:with-gl-context (gl-context window)
          (with-buffers (buffers :count 1)
            (with-shaders (shaders program :shader-list '("test.vert" "test.frag") :dir (asdf:system-source-directory :cl-foo))
              (sdl2:gl-make-current window gl-context)
              (sdl2:hide-cursor)
              (gl:enable :depth-test)
              (gl:clear-color 19/255 19/255 39/255 1.0)
              (gl:clear :color-buffer)
              (let ((coords (make-gl-array :float #(0.0 1.0 -1.0
                                                    1.0 1.0 -1.0
                                                    1.0 0.0 -1.0
                                                    0.0 0.0 -1.0
                                                    0.0 1.0 -1.0))))
                (gl:use-program program)
                (gl:bind-buffer :array-buffer (nth 0 buffers))
                (gl:buffer-data :array-buffer :static-draw coords)
  