anchor.diff:  	 (start-points (mapcar #'first submatrix-instructions)))
       ;; If submatrix-dimensions is nil, the array has one element and we should just
       ;; pass things along to regular old aref.
  -    (if (not (every (lambda (a) (= 1 a)) submatrix-dimensions))
  +    (if (not (every (lambda (a) (= 1 (the fixnum a))) submatrix-dimensions))
   	(reshape-matrix
   	 (with-result (submatrix submatrix-dimensions (array-element-type matrix))
   	   (do-matrix (submatrix indices)
  
positive.code: 	(apply #'aref matrix start-points))))
  
  (defun (setf mref) (source-matrix target-matrix &rest subscripts)
    (let* ((submatrix-instructions
  	  (%submatrix-instructions (array-dimensions target-matrix) subscripts))
  	 (submatrix-dimensions
  
negative.code: 
  (defun mref (matrix &rest subscripts)
    "Functions like (aref), but accepts ranges or T and returns a submatrix of matrix."
    (declare (optimize speed space (safety 0)))
    (let* ((submatrix-instructions
  	  (%submatrix-instructions (array-dimensions matrix) subscripts))
  	 (submatrix-dimensions
  