From: Stefan Monnier <monnier@IRO.UMontreal.CA>
To: Leo Liu <sdl.web@gmail.com>
Cc: 19670@debbugs.gnu.org
Subject: bug#19670: 24.4; pcase-let bug?
Date: Mon, 26 Jan 2015 17:59:09 -0500 [thread overview]
Message-ID: <jwv61btm9ub.fsf-monnier+emacsbugs@gnu.org> (raw)
In-Reply-To: <m2lhkpr513.fsf@gmail.com> (Leo Liu's message of "Mon, 26 Jan 2015 22:27:20 +0800")
> It seems to make more sense for pcase-let to signal an error or bind X
> to nil. WDYT?
Signaling an error would be fine. But it significantly increases the
macro-expanded code size (i.e. it's a lot less efficient).
Defaulting to binding all vars to nil in case of match failure seems
like an even more surprising behavior than what we have now.
The current pcase-let (and pcase-dolist) is meant as a "destructuring"
operation: it doesn't *check* anything, it just accesses subelements of
a structure.
Stefan
prev parent reply other threads:[~2015-01-26 22:59 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-24 2:42 bug#19670: 24.4; pcase-let bug? Leo Liu
2015-01-24 5:07 ` Stefan Monnier
2015-01-26 14:27 ` Leo Liu
2015-01-26 22:59 ` Stefan Monnier [this message]
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