anchor.diff:  		  seq))))
   
   (defun trim-head (obj seq &key (test #'eql))
  -  (when (< 0 (length seq))
  +  (when (integer< 0 (length seq))
       (if (funcall test obj (elt seq 0))
   	    (trim-head obj
   				   (subseq seq 1)
  
positive.code: 
  (defun trim-tail (obj seq &key (test #'eql))
    (let len (length seq)
  	(when (< 0 len)
        (if (funcall test obj (elt seq (integer-1- len)))
  	      (trim-tail obj
  				     (subseq seq 0 (integer-1- len))
  
negative.code:   "Trim start and end of sequence where element is equal to 'obj'."
    (and seq
  	   (if (integer< 0 (length seq))
    		   (trim-tail obj (trim-head obj seq :test test) :test test)
  		   seq)))
  
  (define-test "TRIM-HEAD works"
    ((trim-head #\  "  "))
  