From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Michael Heerdegen <michael_heerdegen@web.de>
Cc: emacs-devel@gnu.org
Subject: Re: gv-exander for 'list'
Date: Tue, 19 Mar 2019 20:38:00 -0400 [thread overview]
Message-ID: <jwvmulqs86h.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <87sgviqys2.fsf@web.de> (Michael Heerdegen's message of "Tue, 19 Mar 2019 23:34:21 +0100")
>> > +(put 'list 'gv-expander
>> > + (lambda (do &rest elt-places)
>> > + ;; FIXME: when using this with letf people would expect this to
>> > + ;; create local bindings
>>
>> Not sure what you mean by this FIXME.
>
> I mean that something like
>
> (cl-letf (((list a) (list 1)))
> a)
>
> errors unless variable a is already bound.
Oh, right, that too.
> I think I just would want simple variables in `list' treated the same way.
Indeed, but the GV infrastructure doesn't offer any way for cl-letf to
do that correctly (short of ad-hoc hacks that special-case `list`).
There are other GVs where `cl-letf` would like to do something a bit
different than just "get...set". E.g. for buffer-modified-p the setter
should be restore-buffer-modified-p when used in `cl-letf`. I haven't
spent much time trying to solve this problem, tho, because `cl-letf` is
not that important in my opinion.
Personally, I wrote "debatable" for the `cons` and `logand` gv-expanders
but I think they're undesirable. Of the two the `logand` is
probably the most useful one (because `logand` can be considered as
a form of projection, like `aref`, `nth`, `car`, ... whereas `cons`
really doesn't fit the pattern).
Stefan
next prev parent reply other threads:[~2019-03-20 0:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-19 16:39 gv-exander for 'list' Michael Heerdegen
2019-03-19 18:41 ` Stefan Monnier
2019-03-19 22:34 ` Michael Heerdegen
2019-03-20 0:38 ` Stefan Monnier [this message]
2019-03-20 18:15 ` Michael Heerdegen
2019-03-20 19:06 ` Stefan Monnier
2019-03-20 20:03 ` Michael Heerdegen
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