GNU bug report logs - #35710
26.1; incomplete mapconcat description string

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

From: phs <phs <at> lsv.fr>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.1; incomplete mapconcat description string
Date: Mon, 13 May 2019 10:43:48 +0200

In my v26.1, the description string for mapconcat is

   mapconcat is a built-in function in ‘src/fns.c’.

   (mapconcat FUNCTION SEQUENCE SEPARATOR)

   Apply FUNCTION to each element of SEQUENCE, and concat the results as
strings.
   In between each pair of results, stick in SEPARATOR.  Thus, " " as
   SEPARATOR results in spaces between the values returned by FUNCTION.
   SEQUENCE may be a list, a vector, a bool-vector, or a string.

The description does not say what is accepted for SEPARATOR, it only
gives an example.

By playing around a bit, it turns out that SEPARATOR can be a string
(obviously), a list of chars, a vector of chars, the empty bool-vector
but not any other bool-vector.

It is not clear why these possibilities are offered while some are not
(e.g., why not make SEPARATOR optional?). This is one more reason to
make the description string explicit about what is allowed.
-- 
Philippe SCHNOEBELEN,       	
"Algebraic symbols are used when you do not know what you are talking about"

Message #8 received at 35710 <at> debbugs.gnu.org (full text, mbox):

From: Noam Postavsky <npostavs <at> gmail.com>
To: phs <phs <at> lsv.fr>
Cc: 35710 <at> debbugs.gnu.org
Subject: Re: bug#35710: 26.1; incomplete mapconcat description string
Date: Mon, 13 May 2019 08:02:44 -0400

phs <phs <at> lsv.fr> writes:

> In my v26.1, the description string for mapconcat is
>
>    mapconcat is a built-in function in ‘src/fns.c’.
>
>    (mapconcat FUNCTION SEQUENCE SEPARATOR)
>
>    Apply FUNCTION to each element of SEQUENCE, and concat the results as
> strings.
>    In between each pair of results, stick in SEPARATOR.  Thus, " " as
>    SEPARATOR results in spaces between the values returned by FUNCTION.
>    SEQUENCE may be a list, a vector, a bool-vector, or a string.
>
> The description does not say what is accepted for SEPARATOR, it only
> gives an example.

It mentions concat, which is what determines what is acceptable.  I
agree it could be made more explicit though.

Message #11 received at 35710 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Noam Postavsky <npostavs <at> gmail.com>
Cc: phs <at> lsv.fr, 35710 <at> debbugs.gnu.org
Subject: Re: bug#35710: 26.1; incomplete mapconcat description string
Date: Mon, 13 May 2019 17:14:52 +0300

> From: Noam Postavsky <npostavs <at> gmail.com>
> Date: Mon, 13 May 2019 08:02:44 -0400
> Cc: 35710 <at> debbugs.gnu.org
> 
> >    (mapconcat FUNCTION SEQUENCE SEPARATOR)
> >
> >    Apply FUNCTION to each element of SEQUENCE, and concat the results as
> > strings.
> >    In between each pair of results, stick in SEPARATOR.  Thus, " " as
> >    SEPARATOR results in spaces between the values returned by FUNCTION.
> >    SEQUENCE may be a list, a vector, a bool-vector, or a string.
> >
> > The description does not say what is accepted for SEPARATOR, it only
> > gives an example.
> 
> It mentions concat, which is what determines what is acceptable.  I
> agree it could be made more explicit though.

The manual does spell that out, we could simply add that to the doc
string.

Message #14 received at 35710 <at> debbugs.gnu.org (full text, mbox):

From: phs <phs <at> lsv.fr>
To: 35710 <at> debbugs.gnu.org
Subject: Re: bug#35710: Acknowledgement (26.1; incomplete mapconcat
 description string)
Date: Tue, 14 May 2019 10:14:02 +0200

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

Thanks for the explanations, I never realized that concat was so
versatile (and I'm an emacs lover since 1983). Live and learn ...

Here is a suggested replacement for the documentation string (patch
attached). It produces

	Apply FUNCTION to each element of SEQUENCE, and concat the results as
strings.
	In between each pair of results, stick in SEPARATOR.  Thus, " " as
	SEPARATOR results in spaces between the values returned by FUNCTION.
	SEQUENCE may be a list, a vector, etc. see ‘mapcar’.
	SEPARATOR and all values returned by FUNCTION must be accepted by ‘concat’.

--phs

[mapconcat-descr.patch (text/plain, attachment)]

Message #19 received at 35710-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: phs <at> lsv.fr
Cc: 35710-done <at> debbugs.gnu.org
Subject: Re: bug#35710: Acknowledgement (26.1;
 incomplete mapconcat description string)
Date: Fri, 07 Jun 2019 16:02:08 +0300

> From: phs <phs <at> lsv.fr>
> Date: Tue, 14 May 2019 10:14:02 +0200
> 
> Thanks for the explanations, I never realized that concat was so
> versatile (and I'm an emacs lover since 1983). Live and learn ...
> 
> Here is a suggested replacement for the documentation string (patch
> attached). It produces
> 
> 	Apply FUNCTION to each element of SEQUENCE, and concat the results as
> strings.
> 	In between each pair of results, stick in SEPARATOR.  Thus, " " as
> 	SEPARATOR results in spaces between the values returned by FUNCTION.
> 	SEQUENCE may be a list, a vector, etc. see ‘mapcar’.
> 	SEPARATOR and all values returned by FUNCTION must be accepted by ‘concat’.

Thanks, I fixed the doc string in a slightly different way.  The fix
will be in Emacs 26.3.  I'm therefore marking this bug done.

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