From: Alan Mackenzie <acm@muc.de>
To: Geoff Gole <geoffgole@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Idempotency of add-hook wrt lambda expressions
Date: Thu, 5 Mar 2009 16:12:06 +0000 [thread overview]
Message-ID: <20090305161206.GA1855@muc.de> (raw)
In-Reply-To: <f5bc73230903040410q43a27bc3tc473b352d05e5aa5@mail.gmail.com>
Hi, Geoff, Hi, Emacs!
On Wed, Mar 04, 2009 at 09:10:45PM +0900, Geoff Gole wrote:
> Say a file contains an add-hook form with a lambda argument:
> (add-hook 'foo-mode (lambda () (bar)))
> Annoyingly, the function will be added to the hook twice if the file
> is byte compiled, loaded, then reevaluated (such as with eval-buffer).
> This can be worked around in any number of ways (don't byte compile,
> don't use lambdas in hooks, restart emacs on every change), but I
> wonder if add-hook can be made to do the right thing.
That begs the question as to what the Right Thing actually is. Surely
this is a case of "you asked for it, you got it".
Also, is there really anything special about hooks here? You're going to
be having this sort of problem wherever you use a lambda when you "really
ought" to be using a symbol.
> One way is to change the hook membership test from:
> (member function hook-value)
> to something like
> (ignore-errors
> (let ((bc-function (byte-compile function)))
> (or (member function hook-value)
> (member bc-function hook-value))))
> But that's pretty horrible. In any case, if there is no fix shouldn't
> this wrinkle be mentioned in the add-hook docstring?
No, it's not "pretty horrible", it's utterly horrific. ;-)
I'm not convinced anything's really needed in the add-hook docstring or
manual entry, but if so, I'd suggest something along the lines "you'd
best use a symbol here unless you really know what you're doing".
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2009-03-05 16:12 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-04 12:10 Idempotency of add-hook wrt lambda expressions Geoff Gole
2009-03-04 14:18 ` Stefan Monnier
2009-03-04 20:13 ` xah lee
2009-03-04 21:23 ` Stefan Monnier
2009-03-04 21:27 ` Lennart Borgman
2009-03-05 17:22 ` M Jared Finder
2009-03-04 21:00 ` David Reitter
2009-03-05 1:27 ` Stephen J. Turnbull
2009-03-05 1:54 ` Stefan Monnier
2009-03-05 8:23 ` Geoff Gole
2009-03-05 9:49 ` David Kastrup
2009-03-05 11:41 ` tomas
2009-03-05 11:53 ` Geoff Gole
2009-03-05 16:45 ` Alan Mackenzie
2009-03-05 16:33 ` Helmut Eller
2009-03-05 16:38 ` Stefan Monnier
2009-03-05 16:50 ` Geoff Gole
2009-03-05 16:38 ` Alan Mackenzie
2009-03-05 20:44 ` Reiner Steib
2009-03-05 20:59 ` Edward O'Connor
2009-03-05 21:08 ` Reiner Steib
2009-03-06 9:36 ` David Kastrup
2009-03-05 16:12 ` Alan Mackenzie [this message]
2009-03-05 16:37 ` Stefan Monnier
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