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Re: Idempotency of add-hook wrt lambda expressions
From: |
Alan Mackenzie |
Subject: |
Re: Idempotency of add-hook wrt lambda expressions |
Date: |
Thu, 5 Mar 2009 16:12:06 +0000 |
User-agent: |
Mutt/1.5.9i |
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).
- Re: Idempotency of add-hook wrt lambda expressions, (continued)
- Re: Idempotency of add-hook wrt lambda expressions, Geoff Gole, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, Alan Mackenzie, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, Helmut Eller, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, Stefan Monnier, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, Geoff Gole, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, Alan Mackenzie, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, Reiner Steib, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, Edward O'Connor, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, Reiner Steib, 2009/03/05
- Re: Idempotency of add-hook wrt lambda expressions, David Kastrup, 2009/03/06
Re: Idempotency of add-hook wrt lambda expressions,
Alan Mackenzie <=