From: Andreas Schwab <schwab@suse.de>
Cc: emacs-devel@gnu.org
Subject: Re: a question about `,' in backquote
Date: Sun, 24 Apr 2005 20:49:53 +0200 [thread overview]
Message-ID: <jeis2c1032.fsf@sykes.suse.de> (raw)
In-Reply-To: <20050425.024959.172916653.jet@gyve.org> (Masatake YAMATO's message of "Mon, 25 Apr 2005 02:49:59 +0900 (JST)")
Masatake YAMATO <jet@gyve.org> writes:
> I found a following line in the definition of `tags-search':
>
> (setq tags-loop-scan `(re-search-forward ',regexp nil t)
>
> Could you tell me why "'" is needed before "," ?
Because the form is passed to eval, which evaluates the function arguments
before applying them. Thus without the quote it would effectively be
doing (eval regexp), which is not what is wanted. Of course, the only
valid type of this argument is a string which is self-evaluating, but you
don't want to evaluate arbitrary values in the error case.
Andreas.
--
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
next prev parent reply other threads:[~2005-04-24 18:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-24 17:49 a question about `,' in backquote Masatake YAMATO
2005-04-24 18:49 ` Andreas Schwab [this message]
2005-04-25 6:19 ` Masatake YAMATO
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