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From: Barry Fishman <barry_fishman@att.net>
Subject: Re: elisp macros problem
Date: Tue, 27 Jul 2004 23:22:42 GMT	[thread overview]
Message-ID: <m3hdrtyr2a.fsf@ecube.site> (raw)
In-Reply-To: x5zn5lvs43.fsf@lola.goethe.zz

David Kastrup <dak@gnu.org> writes:

> Lowell Kirsh <lkirsh@cs.ubc.ca> writes:
>
>> This still doesn't seem to work. With the following defun and call:
>> 
>> (defmacro my-add-hooks (hooks &rest body)
>>    `(dolist (hook ',hooks)
>>       (my-add-hook hook ,@body)))
>> 
>> (my-add-hooks (inferior-lisp lisp emacs-lisp lisp-interaction)
>>                (imenu-add-to-menubar "Symbols"))
>> 
>> > you hoping to achieve that you would not be better off doing by a
>> > proper function instead of a macro?
>
> In short, I still consider this sort of thing a crock, since you'd be
> better off using a function instead of a macro.  You are unable to
> comprehend what your macros do, and it shows.  Macros are just not
> sensible for this sort of thing.  Use functions instead.  You'll need
> to use some quotes at the outer level, but you'll understand what
> happens.
>
> To fix the above, you'd need to write something like
>
> (defmacro my-add-hooks (hooks &rest body)
>    (dolist (hook hooks)
>       `(my-add-hook ,hook ,@body)))


The body of the defmacro has to return some code.  The dolist
will return just NIL.

Assuming that you want my-add-hooks to create a series of my-add-hook
calls, one would need something like:

(defmacro my-add-hooks (hooks &rest body)
   (cons 'progn (mapcar (lambda (h) `(my-add-hook ,h ,@body)) hooks)))

Its usually easier to do the work in a function and use a macro to
create the syntax you want.  For example, using a function like:

(defun my-add-hooks-fn (hooks func)
  (dolist (hook hooks)
    (add-hook (intern (concat (symbol-name hook) "-mode-hook")) func)))

One can give it the syntax you want with a macro like:

(defmacro my-add-hooks (hooks &rest body)
  `(my-add-hooks-2 ',hooks (lambda () ,@body)))

This has the advantage of creating a single lambda function rather
than multiple lambda functions with the same contents.

This also allows one to build a more complex my-add-hooks-fn without
dealing with the extra complexity of structuring it as a macro.

-- 
Barry Fishman

      parent reply	other threads:[~2004-07-27 23:22 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-07-24 18:39 elisp macros problem Lowell Kirsh
2004-07-24 19:00 ` David Kastrup
2004-07-24 22:08   ` Lowell Kirsh
2004-07-24 23:41     ` David Kastrup
2004-07-25  1:58       ` Lowell Kirsh
2004-07-25 10:59         ` Kalle Olavi Niemitalo
2004-07-24 19:15 ` Barry Margolin
2004-07-24 19:59   ` Pascal Bourguignon
2004-07-24 20:50     ` David Kastrup
2004-07-24 21:49       ` Lowell Kirsh
2004-07-26  1:35 ` Lowell Kirsh
2004-07-26  1:55   ` Rahul Jain
2004-07-26  2:53     ` Lowell Kirsh
2004-07-26  4:05       ` Pascal Bourguignon
2004-07-26  4:13         ` Lowell Kirsh
2004-07-26  2:54     ` Lowell Kirsh
2004-07-26 22:16       ` Kalle Olavi Niemitalo
2004-07-26 22:58       ` Kevin Rodgers
2004-07-26  2:03   ` Barry Margolin
2004-07-26  3:06     ` Lowell Kirsh
2004-07-26  4:49       ` Barry Margolin
2004-07-26  5:20         ` Pascal Bourguignon
2004-07-26  6:10       ` Oliver Scholz
2004-07-26  5:55   ` David Kastrup
2004-07-27  6:38     ` Lowell Kirsh
2004-07-27  6:54     ` Lowell Kirsh
2004-07-27  7:14       ` David Kastrup
2004-07-27  8:10         ` Lowell Kirsh
2004-07-27 12:05           ` Pascal Bourguignon
2004-07-28  5:03             ` Rob Warnock
2004-07-31 20:46             ` Lowell Kirsh
2004-08-03 18:44               ` Michael Slass
2004-07-27 23:22         ` Barry Fishman [this message]

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