From: Stefan Monnier <monnier@IRO.UMontreal.CA>
To: Michael Heerdegen <michael_heerdegen@web.de>
Cc: Andreas Schwab <schwab@suse.de>, Emacs Development <emacs-devel@gnu.org>
Subject: Re: Understanding macroexp.el
Date: Wed, 18 Nov 2015 08:36:52 -0500 [thread overview]
Message-ID: <jwvlh9vmnz9.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <87d1v7cy4w.fsf@web.de> (Michael Heerdegen's message of "Wed, 18 Nov 2015 13:03:59 +0100")
>> For byte-compiled code there should be no difference between the two
>> expansions.
> What's the use of `macroexp-unprogn' then at all?
It's when you care to generate slightly cleaner code it's easy to do so.
It usually doesn't really matter much.
> Or does it make a difference in other cases?
I can't remember exactly what motivated me to introduce
macroexp-unprogn, but I don't think it was a strong need.
I can retroactively come up with scenarios where it could make
a difference, but they all seem reasonably infrequent.
E.g. (+ 1 2) will be optimized to 3, but (+ 1 (progn 2)) won't.
Stefan
next prev parent reply other threads:[~2015-11-18 13:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-18 10:32 Understanding macroexp.el Michael Heerdegen
2015-11-18 11:37 ` Andreas Schwab
2015-11-18 12:03 ` Michael Heerdegen
2015-11-18 13:36 ` Stefan Monnier [this message]
2015-11-18 13:40 ` Stefan Monnier
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