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Re: Change a symbol's plist member with (let ...)?
From: |
Thorsten Jolitz |
Subject: |
Re: Change a symbol's plist member with (let ...)? |
Date: |
Fri, 14 Mar 2014 23:25:10 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) |
Nicolas Richard <theonewiththeevillook@yahoo.fr> writes:
> Thorsten Jolitz <tjolitz@gmail.com> writes:
>> #+begin_src emacs-lisp
>> (plist-get (symbol-plist 'outline-mode)
>> 'derived-mode-parent)
>> #+end_src
>>
>
> (get 'outline-mode 'derived-mode-parent) looks better to me.
>
>> For the sake of this example, say I want to "con" the function
>> `derived-mode-p' and make it believe outline-mode is actually derived
>> from lisp-mode (or so ...).
>>
>> How to do this with working code (not pseudo-code)?
>
> I'm in message-mode right now, and :
> (derived-mode-p 'text-mode)
> returns: text-mode
>
> But
> (letf (((get major-mode 'derived-mode-parent) 'special-mode))
> (derived-mode-p 'text-mode))
> returns nil.
I have to get more involved with this cl stuff it seems ...
> You could also let-bind major-mode to whatever the code you're calling
> expects.
>
>> Or do I have to do it the pedestrian way: do plist-get first, store the
>> original value, do plist-put with the new value, call ad-do-it, and then
>> restore the original value again with plist-put?
>
> If you already know what you want the function to return, you could
> simply make
> the advice return that value and not call ad-do-it at all.
yes, I just figured out that a simple (conditional) after advice that sets
ad-return-value to t is all I need.
Thanks for the tips.
--
cheers,
Thorsten