From: Eric Abrahamsen <eric@ericabrahamsen.net>
To: help-gnu-emacs@gnu.org
Subject: Re: watching for variable assignment
Date: Fri, 21 Mar 2014 18:26:01 +0800 [thread overview]
Message-ID: <874n2rhmpy.fsf@ericabrahamsen.net> (raw)
In-Reply-To: jwv61nmcj6e.fsf-monnier+gmane.emacs.help@gnu.org
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> No, this isn't going to work -- the only way I could find the code
>> that's resetting the variable would be to instrument it directly,
>> which would require knowing which code it was in the first place.
>> Not much use!
>
> FWIW, I think I'd accept a patch which adds support for "watchers" on
> symbols (by extending the read-only bit to 2 bits, so we can
> distinguish a "really read-only symbol" from a "symbol with watchers").
>
>> I've got git emacs installed on my system, and I think the newer version
>> of advising functions might work better. I'm hoping that if I add a
>> function to "setq" with the :before key, I can avoid the infinite loop
>> problem.
>
> No, you can't advise special forms (and even if you changed nadvice.el to
> try and support it, it still wouldn't apply to byte-compiled code).
>
>> I read the manual, and found it pretty unhelpful on the question of how
>> to tell it what function you're actually trying to advise. A "setf-able
>> place" doesn't mean much to me when I'm just trying to hijack "setq" and
>> check its args.
>
> Can you point to the offending documentation (it's still in the process
> of being written, so it would be helpful).
> I don't see any "setf-able" anywhere, but FWIW such a thing is also
> called "an lvalue" in other languages.
I saw "Generalized Variable" in the first paragraph, and in my brain I
conflate "generalized variable" with "setf-able place", probably
incorrectly.
FWIW, I updated git emacs recently. The docs seem to have been greatly
expanded, and now make a lot of sense.
E
next prev parent reply other threads:[~2014-03-21 10:26 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-10 9:21 watching for variable assignment Eric Abrahamsen
2014-03-10 9:29 ` Jambunathan K
2014-03-10 9:59 ` Eric Abrahamsen
2014-03-10 10:00 ` Nicolas Richard
2014-03-10 10:09 ` Eric Abrahamsen
2014-03-10 10:35 ` Jambunathan K
2014-03-10 10:48 ` Jambunathan K
2014-03-10 11:23 ` Eric Abrahamsen
2014-03-10 10:54 ` Eric Abrahamsen
2014-03-10 11:08 ` Jambunathan K
2014-03-10 11:38 ` Jambunathan K
2014-03-10 10:35 ` Eric Abrahamsen
2014-03-10 13:06 ` Stefan Monnier
2014-03-21 10:26 ` Eric Abrahamsen [this message]
2014-03-21 12:21 ` Stefan
2014-03-10 19:56 ` Michael Heerdegen
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