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From: "rgb" <rbielaws@i1.net>
Subject: Re: Defadvice use
Date: 18 Apr 2005 17:15:41 -0700	[thread overview]
Message-ID: <1113869741.838603.250620@o13g2000cwo.googlegroups.com> (raw)
In-Reply-To: <87y8bfzx9z.fsf-monnier+gnu.emacs.help@gnu.org>

Stefan Monnier wrote:
> > Doesn't (let (bookmark-bmenu-other-window) ...) have limited life.
>
>   (let (bookmark-bmenu-other-window) ...)
>
> only affects the bookmark-bmenu-other-window *variable*, not the
> bookmark-bmenu-other-window function.
>

If that isn't a bug waiting to happen I don't know what is.
You appear to be asserting that it's documented to work that
way but I'd counter with 2 arguments.

1.  The `feature' is only _implied_, not documented.  There is
    no mention in any Elisp manual section that covers plists
    or symbol function cells about this behavior.

2.  The `feature' invalidates much of the documented behavior of
    symbols unless you know how the symbol was created.

Look at this:

(defun test1 ()
  (let (a01)
    (put 'a01 'hold "this")
    (symbol-plist 'a01)))

(put 'a01 'hold "that") ; insure symbol already exists
(symbol-plist 'a01)
 => (hold "that")       ; value is there as expected

(test1)
 => (hold "this")

(symbol-plist 'a01)
 => (hold "this")       ; external value unexpectedly changed

(unintern "a01")        ; insure it doesn't exist
(symbol-plist 'a01)
 => nil                 ; no error.

(test1)
 => (hold "this")

(symbol-plist 'a01)    ; Given the external value should change
 => nil                ; it now unexpectedly doesn't

It's obviously impossible to easily create any function or
macro that manipulates function or property cells unless you
can guarantee none of the symbols are ever created by let.

Since it appears to be by design, I'd be terribly curious to
see any archive of discussions concerning why this is
appropriate behavior.

  reply	other threads:[~2005-04-19  0:15 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-04-18 12:56 Defadvice use Matthias
2005-04-18 17:11 ` rgb
2005-04-18 17:25   ` Johan Bockgård
2005-04-18 19:05     ` rgb
2005-04-18 19:43       ` Stefan Monnier
2005-04-19  0:15         ` rgb [this message]
2005-04-19  0:28           ` Stefan Monnier
2005-04-19  3:48             ` Mis-features of let (was Defadvice use) rgb
2005-04-19  4:31               ` Mis-features of let Stefan Monnier
2005-04-19  6:38                 ` rgb
2005-04-19 12:21                   ` Stefan Monnier
2005-04-19 20:31                     ` rgb
2005-04-19 21:45                       ` David Kastrup
2005-04-19 12:55                   ` Barry Margolin
2005-04-19 20:31                     ` rgb
2005-04-20  4:12                       ` Barry Margolin
2005-04-19 21:10                     ` rgb
2005-04-19 21:57                       ` Kevin Rodgers
2005-04-19 22:00                       ` David Kastrup
2005-04-20  1:04                         ` rgb
2005-04-20 10:04                           ` David Kastrup
2005-04-20 11:57                             ` Stefan Monnier
2005-04-20 14:41                           ` Thien-Thi Nguyen
2005-04-19  9:41               ` Thien-Thi Nguyen
2005-04-19  5:07           ` Defadvice use Barry Margolin
2005-04-18 17:52 ` Stefan Monnier
2005-04-18 21:07   ` Matthias
2005-04-18 23:20     ` Stefan Monnier
2005-04-18 20:28 ` Kevin Rodgers

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