GNU bug report logs - #34852
26.1; seq-intersection ignores nil as element

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Message #68 received at 34852 <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: "Miguel V. S. Frasson" <mvsfrasson <at> gmail.com>
Cc: "Basil L. Contovounesios" <contovob <at> tcd.ie>,
 Nicolas Petton <nicolas <at> petton.fr>, Stefan Monnier <monnier <at> iro.umontreal.ca>,
 34852 <at> debbugs.gnu.org
Subject: Re: bug#34852: 26.1; seq-intersection ignores nil as element
Date: Fri, 15 Mar 2019 00:15:20 +0100

"Miguel V. S. Frasson" <mvsfrasson <at> gmail.com> writes:

> Hi
>
> In any case, of another implementation for seq-intersection or not, I
> think that the solution from Stefan should be implemented anyway
> because
>
> * it makes seq-contains provide a useful return value when ELT=nil, so
> it is a good exception; If ELT=nil, seq-contains currently returns nil
> anyway;
>
> * it makes seq-contains become a real predicate function, making it
> more useful;
>
> * since seq-contains has been used as predicate before, it is
> unpredictable which code uses it out of official repositories, so this
> fix potentially fixes other code.

BTW, another (alternative) alternative would be to make it return
(list ELT).  That would be a bit less backward-compatible, but a
bit more consistent.

Michael.

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