From: "Herbert Euler" <herberteuler@hotmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Macro vs Function
Date: Thu, 13 Apr 2006 10:17:01 +0800 [thread overview]
Message-ID: <BAY112-F22119603F2C3F04618BAB6DAC30@phx.gbl> (raw)
In-Reply-To: <85irpe20hq.fsf@lola.goethe.zz>
>From: David Kastrup <dak@gnu.org>
>To: "Herbert Euler" <herberteuler@hotmail.com>
>CC: emacs-devel@gnu.org
>Subject: Re: Macro vs Function
>Date: Wed, 12 Apr 2006 18:59:45 +0200
>
>"Herbert Euler" <herberteuler@hotmail.com> writes:
>
> >>From: David Kastrup <dak@gnu.org>
> >>To: "Herbert Euler" <herberteuler@hotmail.com>
> >>CC: emacs-devel@gnu.org
> >>Subject: Re: Macro vs Function
> >>Date: Wed, 12 Apr 2006 17:29:40 +0200
> >>
> >>Why are you bothering with "apply" in the first place? It does not
> >>look like you have any need for it. Just write
> >
> > Because func is supposed to be a variable set by, for instance,
> >
> > (setq f '+)
> >
> > And '+ is just for testing purpose.
>
>Could you _please_ quote the relevant definitions when answering? It
>causes a lot of extra work if I have to go constantly to previous
>parts of the thread to dig them out.
I'm sorry.
>I still don't see why you can't just write
>
>(defmacro xgp-casi2-safe-call-iter (func largs)
> (and largs
> `(condition-case nil
> (funcall ,func ,@(car largs))
> (error (xgp-casi2-safe-call-iter ,func ,(cdr largs))))))
>
>Or, if you really insist on "apply",
>
>(defmacro xgp-casi2-safe-call-iter (func largs)
> (and largs
> `(condition-case nil
> (apply ,func (list ,@(car largs)))
> (error (xgp-casi2-safe-call-iter ,func ,(cdr largs))))))
Yes, these two both work. When I wrote the "complete
and utter contorted mess":
>(defmacro xgp-casi2-safe-call-iter (func largs)
> (if largs
> `(condition-case nil
> (apply ,func ,((lambda (a) `(quote ,(car a))) largs))
> (error (xgp-casi2-safe-call-iter ,func ,(cdr largs))))
> 'nil))
I didn't understand the mechanism of macros. If I'm writing
them now, I too will write simple ones like what Stuart D.
Herring and you write.
Thank you very much, for making me understand how macro
works.
Sincerely yours,
Guanpeng Xu
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next prev parent reply other threads:[~2006-04-13 2:17 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-12 8:22 Macro vs Function Herbert Euler
2006-04-12 9:07 ` David Kastrup
2006-04-12 9:17 ` Herbert Euler
2006-04-12 9:24 ` David Kastrup
2006-04-12 9:39 ` Herbert Euler
2006-04-12 9:53 ` David Kastrup
2006-04-12 10:39 ` Herbert Euler
2006-04-12 11:14 ` Andreas Schwab
2006-04-12 11:56 ` Herbert Euler
2006-04-12 12:08 ` Herbert Euler
2006-04-12 12:19 ` David Kastrup
2006-04-12 13:37 ` Herbert Euler
2006-04-12 13:52 ` David Kastrup
2006-04-12 15:13 ` Herbert Euler
2006-04-12 15:26 ` Stuart D. Herring
2006-04-12 15:54 ` Herbert Euler
2006-04-12 15:29 ` David Kastrup
2006-04-12 15:56 ` Herbert Euler
2006-04-12 16:14 ` Herbert Euler
2006-04-12 16:59 ` David Kastrup
2006-04-13 2:17 ` Herbert Euler [this message]
2006-04-12 12:12 ` David Kastrup
2006-04-12 11:19 ` David Kastrup
-- strict thread matches above, loose matches on Subject: below --
2006-04-12 12:05 Herbert Euler
2006-04-12 12:13 ` David Kastrup
2006-04-12 12:17 ` Herbert Euler
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