anchor.diff:  
   (defun read-pgm-p5 (stream)
     (with-pnm-header t
  -    (loop with size of-type fixnum = (* width height) 
  +    (loop with size of-type fixnum = (* width height)
   	  with result = (make-array `(,height ,width) :element-type '(unsigned-byte 8))
   	  with vec = (make-array `(,size)
   				 :element-type '(unsigned-byte 8)
  
positive.code:    "GRAY-IMAGE-MIN-LEVEL" "GRAY-IMAGE-MIN-LEVEL"
     "TRUECOLOR-IMAGE" "MAKE-TRUECOLOR-IMAGE" "MAKE-3X256-COLOR-IMAGE"
     "COLOR-IMAGE-MIN-LEVEL" "COLOR-IMAGE-MAX-LEVEL"
     "BINARY-IMAGE" "MAKE-BINARY-IMAGE" 
     "RED-COMPONENT" "GREEN-COMPONENT" "BLUE-COMPONENT"
     "COLORMAP-IMAGE"
     "SPECTRAL-IMAGE"))
  
negative.code: (defun write-ppm-p3 (stream picture)
    (with-write-pnm-loop (3 255)
      (let ((rgb (aref picture r c)))
        (format stream "~A ~A ~A~%"
  	      (red-component rgb)
  	      (green-component rgb)
  	      (blue-component rgb)))))
  
  