anchor.diff:     #'search-backward
      ""))
   
  -(define-command isearch-backward () ()
  +(define-command isearch-backward (&optional prompt) ((list nil))
     (isearch-start
  -   "ISearch: "
  +   (or prompt "ISearch: ")
      (lambda (point str)
        (search-backward (or (character-offset point (length str))
                             point)
  
positive.code:    #'search-backward
     ""))
  
  (define-command isearch-forward-regexp () ()
    (isearch-start "ISearch Regexp: "
                   #'search-forward-regexp
                   #'search-forward-regexp
                   #'search-backward-regexp
                   ""))
  
  (define-command isearch-backward-regexp () ()
    (isearch-start "ISearch Regexp: "
                   #'search-backward-regexp
                   #'search-forward-regexp
                   #'search-backward-regexp
                   ""))
  
  (define-command isearch-forward-symbol () ()
    (isearch-start "ISearch Symbol: "
                   #'search-forward-symbol
                   #'search-forward-symbol
                   #'search-backward-symbol
                   ""))
  
  (define-command isearch-backward-symbol () ()
    (isearch-start "ISearch Symbol: "
                   #'search-backward-symbol
                   #'search-forward-symbol
                   #'search-backward-symbol
  
negative.code:            :isearch-prev
             :isearch-yank
             :isearch-self-insert
             :isearch-replace-highlight
             :isearch-next-highlight
             :isearch-prev-highlight
             :isearch-toggle-highlighting
             :read-query-replace-args
             :isearch-toggle-highlighting
             :query-replace
  