From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Nathan Trapuzzano <nbtrap@nbtrap.com>
Cc: emacs-devel@gnu.org
Subject: Re: Double unquote/unquote-splicing
Date: Tue, 05 Nov 2013 14:14:52 -0500 [thread overview]
Message-ID: <jwvvc06fz8z.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <87fvrahovc.fsf@nbtrap.com> (Nathan Trapuzzano's message of "Tue, 05 Nov 2013 10:03:51 -0500")
> I don't think the special syntax does make that clear.
You can't use that special syntax for multi-arg unquote and
unquote/unquote-splicing. So the special syntax makes it clear that
those are expected to take a single arg. And indeed, so far, they
can only take a single arg.
>> Your example was the first concrete example I've seen where such
>> a ,,@foo construct was used and as you've seen it's trivially replaced
>> by ,@(list ,@foo) (which is true because ,foo is equivalent to ,@(list
>> foo).
> Hmm, I'm actually not sure that will always work.
Goes to show again that it's too complex for our own good.
>> So ,,@ is not a very compelling use. Maybe ,@,@ would be more
>> compelling, but I haven't seen any concrete use for it yet, so I can't
>> comment.
> Can't say I know of a good use of ,@,@. That said, I think it would be
> silly for this proposal to stand or fall on that basis.
There's a straightforward rewriting of ",,@", and there's no known use
case for ",@,@" (which AFAIK can be rewritten ",@(append ,@" anyway if
you really need it). It probably doesn't break any code, but I prefer
to keep the rule that unquote/unquote-splicing takes a single argument,
since that's true 99.99% of the time, so while people are likely to
understand the single-arg case, and they're unlikely to understand the
multi-arg case.
Stefan
next prev parent reply other threads:[~2013-11-05 19:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-04 14:03 Double unquote/unquote-splicing Nathan Trapuzzano
2013-11-04 17:27 ` Stefan Monnier
2013-11-04 17:59 ` Nathan Trapuzzano
2013-11-04 18:11 ` Nathan Trapuzzano
2013-11-04 18:33 ` Stefan Monnier
2013-11-04 19:01 ` Drew Adams
2013-11-04 19:09 ` Nathan Trapuzzano
2013-11-04 20:41 ` Stefan Monnier
2013-11-05 15:03 ` Nathan Trapuzzano
2013-11-05 19:14 ` Stefan Monnier [this message]
2013-11-05 4:01 ` Stephen J. Turnbull
2013-11-05 15:22 ` Nathan Trapuzzano
2013-11-05 21:48 ` Stephen J. Turnbull
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