anchor.diff:  
   ;;----------------------------------------------------------------
   
  -(defun get-columns (mat-a)
  +(defn get-columns ((mat-a mat4)) list
     "Return the columns of the matrix as 4 vector4s"
  +  (declare (optimize (speed 3) (safety 1) (debug 1)))
     (list (v! (melm mat-a 0 0)
               (melm mat-a 1 0)
               (melm mat-a 2 0)
  
positive.code: 
  ;;----------------------------------------------------------------
  
  (defun rotation-z (angle)
    "Returns a matrix which would rotate a point around the z axis
     by the specified amount"
    (let ((s-a (sin angle))
          (c-a (cos angle)))
      (make c-a  (cl:- s-a)  0f0  0f0
  
negative.code:                   (z (z axis3))
                    (gxx (cl:* g x x)) (gxy (cl:* g x y)) (gxz (cl:* g x z))
                    (gyy (cl:* g y y)) (gyz (cl:* g y z)) (gzz (cl:* g z z)))
               (make
                (cl:+ gxx c)        (cl:- gxy (cl:* s z))  (cl:+ gxz (cl:* s y)) 0f0
                (cl:+ gxy (cl:* s z))  (cl:+ gyy c)        (cl:- gyz (cl:* s x)) 0f0
                (cl:- gxz (cl:* s y))  (cl:+ gyz (cl:* s x))  (cl:+ gzz c)       0f0
  