From: Lars Ingebrigtsen <larsi@gnus.org>
To: akater <nuclearspace@gmail.com>
Cc: 51412@debbugs.gnu.org, Stefan Monnier <monnier@iro.umontreal.ca>
Subject: bug#51412: 29.0.50; cl--mapcar-many fails inconsistently in the presence of circular lists; other shortcomings
Date: Wed, 14 Sep 2022 20:38:45 +0200 [thread overview]
Message-ID: <87leql3ioa.fsf@gnus.org> (raw)
In-Reply-To: <87ee88dmzb.fsf@gmail.com> (akater's message of "Tue, 26 Oct 2021 11:50:00 +0000")
akater <nuclearspace@gmail.com> writes:
> cl--mapcar-many is used as a backend for implementing several cl-
> functions in cl-extra. To deal with arbitrary number of arguments
> (passed to cl--mapcar-many as list cl-seq), it goes through them all
> whenever there are more than 2, in advance, and attempts to compute the
> minimal length.
>
> This fails if any of the arguments is a circular list.
>
> To reproduce, just evaluate (cl-map 'list #'identity '#1=(a . #1#) nil nil).
Debugger entered--Lisp error: (circular-list (a . #2))
> Note that (cl-map 'list #'identity '#1=(a . #1#) nil) doesn't fail so
> this is at the very least inconsistent. N.B.: CL spec says “Should be
> prepared to signal an error” for improper lists for such functions.
> Long story short, this means circular lists can be supported by CL
> implementations according to CL spec.
It's inconsistent, so that should probably be fixed. But isn't
signalling an error here the right thing to do? But I guess as long as
not all the lists are circular, then it's fine to return something
here...
Perhaps Stafan has some comments; added to the CCs.
prev parent reply other threads:[~2022-09-14 18:38 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-26 11:50 bug#51412: 29.0.50; cl--mapcar-many fails inconsistently in the presence of circular lists; other shortcomings akater
2022-09-14 18:38 ` Lars Ingebrigtsen [this message]
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