anchor.diff:      (:p "Note that the last search engine is the default one. For example, in
   order to make python3 the default, the above code can be slightly modified as
   follows.")
  -        (:pre (:code "
  +    (:pre (:code "
   \(defvar *my-search-engines*
     (list
      '(\"doi\" \"https://dx.doi.org/~a\" \"https://dx.doi.org/\")
  
positive.code:     (:h3 "Custom commands")
      (:p "Creating your own invokable commands is similar to creating a Common
  Lisp function, except the form is " (:code "define-command") " instead of "
          (:code "defun") ". If you want this command to be invokable outside of
          the context of a mode, use " (:code "define-command-global") ".")
      (:p "Example:")
      (:pre (:code
  
negative.code: add the following to your configuration:")
      (:ul
       (:li "vi bindings:"
            (:pre (:code "
  \(define-configuration buffer
    ((default-modes (append '(vi-normal-mode) %slot-default%))))")))
       (:li "Emacs bindings:"
            (:pre (:code "
  \(define-configuration buffer
    ((default-modes (append '(emacs-mode) %slot-default%))))"))))
      (:p "You can create new scheme names with " (:code "keymap:make-scheme-name")
          ".  Also see the " (:code "scheme-name") " class and the "
          (:code "define-scheme") " macro.")
      (:p "To extend the bindings of a specific mode, you can extend the mode with "
          (:code "define-configuration") " and extend its binding scheme with "
          (:code "define-scheme") ". For example:")
      (:pre (:code "
  \(define-configuration base-mode
    ((keymap-scheme
      (define-scheme (:name-prefix \"my-base\" :import %slot-default%)
        scheme:vi-normal
        (list \"g b\" (make-command switch-buffer* ()
                      (switch-buffer :current-is-last-p t)))))))"))
      (:p "The " (:code "override-map") " is a keymap that has priority over
  all other keymaps.  By default, it has few bindings like the one
  for " (:code "execute-command") ".  You can use it to set keys globally:")
      (:pre (:code "
  