From: "Pascal J. Bourguignon" <pjb@informatimago.com>
To: help-gnu-emacs@gnu.org
Subject: Re: flet, cl-flet, cl-letf in 24.3
Date: Sat, 27 Apr 2013 13:46:20 +0200 [thread overview]
Message-ID: <877gjo2o37.fsf@kuiper.lan.informatimago.com> (raw)
In-Reply-To: 098b3b26-6cfa-478b-8870-7a7bdb806611@googlegroups.com
ndemmel@gmail.com writes:
> On Monday, April 22, 2013 3:32:05 PM UTC+2, Stefan Monnier wrote:
>> > as reported here [5], this documentation does not really tell me what to do
>>
>> > if I want to keep relying on the dynamic scoping of flet. A brief google
>>
>> > search [6] leads me to believe that
>>
>>
>>
>> > (cl-letf (((symbol-function 'foo) #'(lambda (...) ...))) ...)
>>
>>
>>
>> > is the suggested solution,
>>
>>
>>
>> That's the case.
>
> Thanks!
>
>>
>> > Does that always have dynamic scope?
>>
>> How could it not?
>>
>
> I'm not sure. What makes you say that?
That's because it's not until run-time that the function slot of the
symbol foo is modified. The _expression_ is evaluated at run-time.
Here we have a literal anonymous function, but it could be any
expression returning a function determined at run-time.
Therefore there's absolutely no way the compiler can know what (foo x)
means inside the cl-letf (apart from the fact that it's a function
call).
Also, since (symbol-function 'foo) is a global place, _while_ the cl-letf
is in effect, (foo x) will call your lambda even outside of the lexical
scope of the cl-letf.
> I can see how a lexical binding
> to a generalized place (not a variable) would not neccessarily make
> sense; is that what you mean?
Indeed.
--
__Pascal Bourguignon__ http://www.informatimago.com/
A bad day in () is better than a good day in {}.
next prev parent reply other threads:[~2013-04-27 11:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-21 7:04 flet, cl-flet, cl-letf in 24.3 ndemmel
2013-04-21 7:41 ` Drew Adams
[not found] ` <mailman.24402.1366530089.855.help-gnu-emacs@gnu.org>
2013-04-21 9:49 ` ndemmel
2013-04-21 16:07 ` Drew Adams
2013-04-22 13:32 ` Stefan Monnier
2013-04-22 15:09 ` Andreas Röhler
[not found] ` <mailman.24438.1366637539.855.help-gnu-emacs@gnu.org>
2013-04-27 11:16 ` ndemmel
2013-04-27 11:46 ` Pascal J. Bourguignon [this message]
2013-04-27 13:52 ` Stefan Monnier
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