anchor.diff:  	(stream (values output nil)))
       (unwind-protect
   	 (progn
  +	   (format stream "~&Date/time: ~a" (date-time-string))
   	   (print-condition error stream)
  -	   (format stream "~&Date/time: ~a" (date-time-string))
   	   (terpri stream)
   	   (print-backtrace-to-stream stream)
   	   (terpri stream)
  
positive.code:    "~@<An unhandled error condition has been signalled:~3I ~a~I~:@>~%~%"
     condition))
    
  (defun print-backtrace (error &key (output nil) (if-exists :append)
  			(verbose nil))
    "Send a backtrace for the error `error` to `output`. 
  
  
negative.code: ;; function
  (eval-when (:compile-toplevel :load-toplevel :execute)
    (when (find-symbol "*DEBUG-PRINT-VARIABLE-ALIST*" :sb-debug)
      (pushnew :sbcl-debug-print-variable-alist *features*)))
  
  #+sbcl
  (defun print-backtrace-to-stream (stream)
    (let (#+:sbcl-debug-print-variable-alist
  	(sb-debug:*debug-print-variable-alist*
  	 (list* '(*print-level* . nil)
  		'(*print-length* . nil)
  		sb-debug:*debug-print-variable-alist*))
  	#-:sbcl-debug-print-variable-alist
  	(sb-debug:*debug-print-level* nil)
  	#-:sbcl-debug-print-variable-alist
  	(sb-debug:*debug-print-length* nil))
      (sb-debug:backtrace most-positive-fixnum stream)))
  
  