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

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Hong Xu <hong <at> topbug.net>
To: bug-gnu-emacs <at> gnu.org
Cc: Hong Xu <hong <at> topbug.net>
Subject: [PATCH] Clarify that mapconcat's FUNCTION can return nil
Date: Wed, 12 Feb 2025 14:27:03 -0800

* src/fns.c (Fmapconcat): Explain that FUNCTION can return nil.
---
 src/fns.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/fns.c b/src/fns.c
index bee44b222c5e..f02a1b6838da 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -3400,9 +3400,11 @@ SEQUENCE may be a list, a vector, a bool-vector, or a string.
 Optional argument SEPARATOR must be a string, a vector, or a list of
 characters; nil stands for the empty string.
 
-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. */)
   (Lisp_Object function, Lisp_Object sequence, Lisp_Object separator)
 {
   USE_SAFE_ALLOCA;
-- 
2.48.1

Message #8 received at 76242 <at> debbugs.gnu.org (full text, mbox):

From: Hong Xu <hong <at> topbug.net>
To: 76242 <at> debbugs.gnu.org
Subject: Re: [PATCH] Clarify that mapconcat's FUNCTION can return nil
Date: Wed, 12 Feb 2025 14:31:31 -0800

[Message part 1 (text/plain, inline)]

On 2025-02-12 Wed 14:27 GMT-08, Hong Xu <hong <at> topbug.net> wrote:

> * src/fns.c (Fmapconcat): Explain that FUNCTION can return nil.
> ---
>  src/fns.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/src/fns.c b/src/fns.c
> index bee44b222c5e..f02a1b6838da 100644
> --- a/src/fns.c
> +++ b/src/fns.c
> @@ -3400,9 +3400,11 @@ SEQUENCE may be a list, a vector, a bool-vector, or a string.
>  Optional argument SEPARATOR must be a string, a vector, or a list of
>  characters; nil stands for the empty string.
>  
> -FUNCTION must be a function of one argument, and must return a value
> + FUNCTION must be a function of one argument, and must return either:

For some reason there is an extra space here. I've corrected this with
the attached patch.

[v2-0001-Clarify-that-mapconcat-s-FUNCTION-can-return-nil.patch (text/x-patch, inline)]

From 42b5c39abd1765efc286178d041c57623d722d0d Mon Sep 17 00:00:00 2001
From: Hong Xu <hong <at> topbug.net>
Date: Wed, 12 Feb 2025 14:25:34 -0800
Subject: [PATCH v2] Clarify that mapconcat's FUNCTION can return nil

* src/fns.c (Fmapconcat): Explain that FUNCTION can return nil.
---
 src/fns.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/fns.c b/src/fns.c
index bee44b222c5e..fc7039c1592b 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -3400,9 +3400,11 @@ SEQUENCE may be a list, a vector, a bool-vector, or a string.
 Optional argument SEPARATOR must be a string, a vector, or a list of
 characters; nil stands for the empty string.
 
-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. */)
   (Lisp_Object function, Lisp_Object sequence, Lisp_Object separator)
 {
   USE_SAFE_ALLOCA;
-- 
2.48.1

[Message part 3 (text/plain, inline)]

-- 
Hong

Message #11 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Hong Xu via "Bug reports for GNU Emacs, the Swiss army knife of text
 editors" <bug-gnu-emacs <at> gnu.org>
Cc: 76242 <at> debbugs.gnu.org, Hong Xu <hong <at> topbug.net>
Subject: Re: bug#76242: [PATCH] Clarify that mapconcat's FUNCTION can return
 nil
Date: Thu, 13 Feb 2025 02:27:52 +0100

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?


Michael.

Message #19 received at 76242 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Michael Heerdegen <michael_heerdegen <at> web.de>
Cc: 76242 <at> debbugs.gnu.org, hong <at> topbug.net
Subject: Re: bug#76242: [PATCH] Clarify that mapconcat's FUNCTION can return
 nil
Date: Thu, 13 Feb 2025 09:57:05 +0200

> 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.

Message #22 received at 76242 <at> debbugs.gnu.org (full text, mbox):

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: Re: 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

Message #25 received at 76242 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefankangas <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>, Michael Heerdegen <michael_heerdegen <at> web.de>
Cc: 76242 <at> debbugs.gnu.org, hong <at> topbug.net
Subject: Re: bug#76242: [PATCH] Clarify that mapconcat's FUNCTION can return
 nil
Date: Thu, 13 Feb 2025 00:29:27 -0800

Eli Zaretskii <eliz <at> gnu.org> writes:

> 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.

LGTM.

Message #30 received at 76242-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Hong Xu <hong <at> topbug.net>
Cc: michael_heerdegen <at> web.de, 76242-done <at> debbugs.gnu.org
Subject: Re: bug#76242: [PATCH] Clarify that mapconcat's FUNCTION can return
 nil
Date: Thu, 13 Feb 2025 11:04:34 +0200

> Date: Thu, 13 Feb 2025 00:27:45 -0800
> From: Hong Xu <hong <at> topbug.net>
> CC: 76242 <at> debbugs.gnu.org
> 
> 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.

> From: Stefan Kangas <stefankangas <at> gmail.com>
> Date: Thu, 13 Feb 2025 00:29:27 -0800
> Cc: 76242 <at> debbugs.gnu.org, hong <at> topbug.net
> 
> Eli Zaretskii <eliz <at> gnu.org> writes:
> 
> > 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.
> 
> LGTM.

Thanks, installed on the emacs-30 release branch, and closing the bug.

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