GNU bug report logs - #76242
[PATCH] Clarify that mapconcat's FUNCTION can return nil

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From: Hong Xu <hong <at> topbug.net>
To: Eli Zaretskii <eliz <at> gnu.org>, Michael Heerdegen <michael_heerdegen <at> web.de>
Cc: 76242 <at> debbugs.gnu.org
Subject: bug#76242: [PATCH] Clarify that mapconcat's FUNCTION can return nil
Date: Thu, 13 Feb 2025 00:27:45 -0800

On February 12, 2025 11:57:05 PM PST, Eli Zaretskii <eliz <at> gnu.org> wrote:
>> Cc: hong <at> topbug.net
>> Date: Thu, 13 Feb 2025 02:27:52 +0100
>> From:  Michael Heerdegen via "Bug reports for GNU Emacs,
>>  the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>
>> 
>> Hong Xu via "Bug reports for GNU Emacs, the Swiss army knife of text
>> editors" <bug-gnu-emacs <at> gnu.org> writes:
>> 
>> > -FUNCTION must be a function of one argument, and must return a value
>> > -  that is a sequence of characters: either a string, or a vector or
>> > -  list of numbers that are valid character codepoints.  */)
>> > + FUNCTION must be a function of one argument, and must return either:
>> > +
>> > +   nil, which is treated as an empty string, or
>> > +   a value that is a sequence of characters, which is either a string,
>> > +   or a vector or list of numbers that are valid character codepoints. */)
>> 
>> I don't understand the rationale.  Isn't nil just one case of an empty
>> sequence of characters?  Why describe it specially?
>
>How about the below instead:
>
>  FUNCTION must be a function of one argument, and must return a value
>    that is a sequence of characters: either a string, or a vector or
>    list of numbers that are valid character codepoints; nil is treated
>    as an empty string.

I agree, this is better.


Hong

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