anchor.diff:    (float-zero (apply-across-elements + ((vc-a vector-a)) 3
   		   (expt vc-a 2))))
   
  -;----------------------------------------------------------------
  +;;---------------------------------------------------------------
   
   (declaim (inline unitp)
   	 (ftype (function ((simple-array single-float (3))) 
  
positive.code:   (declare ((simple-array single-float (3)) vector-a))
    (float-zero (- 1.0 (apply-across-elements + ((vc-a vector-a)) 3
  			  (expt vc-a 2)))))
  ;----------------------------------------------------------------
  
  ;; Would be interesting to see if checking that the arrays
  ;; are not 'eq' first would speed this up 
  (declaim (inline v-eq)
  	 (ftype (function ((simple-array single-float (3)) 
  			   (simple-array single-float (3))) 
  
negative.code: 				       (vc-b vector-b)) 3
      (+ vc-a vc-b)))
  
  ;;---------------------------------------------------------------
  
  ;; Not sure how to optomise this
  (defun v- (&rest vec3s)
  