Subject: Re: bug#34852: 26.1; seq-intersection ignores nil as element

From: Michael Heerdegen <[email-masked]>
Date: Fri, 15 Mar 2019 00:42:39 +0100

Stefan Monnier <[email-masked]> writes:

> > (seq-contains nil '(nil t foo) (lambda (x) t))  ->  nil
> > It returns *nil* if testfn fails, or *nil* (ELT) if it succeds.
>
> Just because it sometimes does doesn't mean it always does:
>
>     (seq-contains '(0 3 4) 1 #'<)
>
> returns 3

Maybe it's too late here, but why is that a counterexample for

> If ELT=nil, seq-contains currently returns nil anyway;"

The first element is returned for that the test succeeds, what's special
about it?  < is not symmetrical, though, so it's a weird kind of
equality test.

Michael.