GNU bug report logs - #79470
[PATCH] backward-sentence: Fix inaccuracy in manual's description

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

From: ERIC Frederickson <ericfrederickson68 <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: [PATCH] backward-sentence: Fix inaccuracy in manual's description
Date: Thu, 18 Sep 2025 23:16:23 -0500

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

Hello everyone,

The patch attached to this message corrects a small inaccuracy in the
description of the 'backward-sentence' command in
doc/emacs/text.texi (Sentences).

When describing the behavior of 'backward-sentence', the manual states
that this command leaves point "just before the first character of the
sentence".  This is incorrect, as 'backward-sentence' actually leaves
point _on_ the first character of the sentence.

When I first saw this, I thought I had to be missing something, but
after reading through adjacent docs to make sure I had the right
interpretation of point being "on" a character vs "before"/"after" it,
and then multi-checking that I wasn't simply misreading the manual, I
came to the conclusion that patching this description to use the word
"on" instead of the words "just before" would be worthwhile.

^L

Also: I hope that I'm not cluttering the mailing list with too many
small patches sent close together.  I've happened to have a good deal
of free time this week and have been enjoying trying to make some
improvements to my favorite program.  If anything I've been doing
lately has been causing too much noise for anyone, please do let me
know what kind of conduct is best appreciated around here, and I'll do
my best to align with that.

Thank you for your time,
--
Eric Frederickson

[0001-backward-sentence-doc-fix.patch (application/octet-stream, attachment)]

Message #8 received at 79470 <at> debbugs.gnu.org (full text, mbox):

From: Manuel Giraud <manuel <at> ledu-giraud.fr>
To: ERIC Frederickson <ericfrederickson68 <at> gmail.com>
Cc: 79470 <at> debbugs.gnu.org
Subject: Re: bug#79470: [PATCH] backward-sentence: Fix inaccuracy in
 manual's description
Date: Fri, 19 Sep 2025 07:49:58 +0200

ERIC Frederickson <ericfrederickson68 <at> gmail.com> writes:

> Hello everyone,
>
> The patch attached to this message corrects a small inaccuracy in the
> description of the 'backward-sentence' command in
> doc/emacs/text.texi (Sentences).
>
> When describing the behavior of 'backward-sentence', the manual states
> that this command leaves point "just before the first character of the
> sentence".  This is incorrect, as 'backward-sentence' actually leaves
> point _on_ the first character of the sentence.

Hi Eric,

I think that "just before" is also correct because the point of
insertion *really is* just before the first character of the sentence.
And IMO, in this regard, "just before" is more precise than "on the
character".

> When I first saw this, I thought I had to be missing something, but
> after reading through adjacent docs to make sure I had the right
> interpretation of point being "on" a character vs "before"/"after" it,
> and then multi-checking that I wasn't simply misreading the manual, I
> came to the conclusion that patching this description to use the word
> "on" instead of the words "just before" would be worthwhile.

Do you have example of such usage of "on"?
-- 
Manuel Giraud

Message #11 received at 79470 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: ERIC Frederickson <ericfrederickson68 <at> gmail.com>
Cc: 79470 <at> debbugs.gnu.org
Subject: Re: bug#79470: [PATCH] backward-sentence: Fix inaccuracy in manual's
 description
Date: Fri, 19 Sep 2025 09:14:25 +0300

> From: ERIC Frederickson <ericfrederickson68 <at> gmail.com>
> Date: Thu, 18 Sep 2025 23:16:23 -0500
> 
> The patch attached to this message corrects a small inaccuracy in the
> description of the 'backward-sentence' command in
> doc/emacs/text.texi (Sentences).
> 
> When describing the behavior of 'backward-sentence', the manual states
> that this command leaves point "just before the first character of the
> sentence".  This is incorrect, as 'backward-sentence' actually leaves
> point _on_ the first character of the sentence.

In Emacs, point cannot be _on_ a character, it is always _between_ two
characters.  The Emacs user manual says:

     By default, the cursor in the selected window is drawn as a solid
  block and appears to be _on_ a character, but you should think of point
  as _between_ two characters; it is situated _before_ the character under
  the cursor.  For example, if your text looks like ‘frob’ with the cursor
  over the ‘b’, then point is between the ‘o’ and the ‘b’.  If you insert
  the character ‘!’ at that position, the result is ‘fro!b’, with point
  between the ‘!’ and the ‘b’.  Thus, the cursor remains over the ‘b’, as
  before.

So you should understand the "before the first character" part of what
the manual says in this context.

So I don't think what the manual says is inaccurate.

> Also: I hope that I'm not cluttering the mailing list with too many
> small patches sent close together.  I've happened to have a good deal
> of free time this week and have been enjoying trying to make some
> improvements to my favorite program.  If anything I've been doing
> lately has been causing too much noise for anyone, please do let me
> know what kind of conduct is best appreciated around here, and I'll do
> my best to align with that.

No problems here, feel free to submit any issue you think is worthy of
discussing.

Message #14 received at 79470 <at> debbugs.gnu.org (full text, mbox):

From: ERIC Frederickson <ericfrederickson68 <at> gmail.com>
To: Manuel Giraud <manuel <at> ledu-giraud.fr>
Cc: 79470 <at> debbugs.gnu.org
Subject: Re: bug#79470: [PATCH] backward-sentence: Fix inaccuracy in manual's
 description
Date: Fri, 19 Sep 2025 13:13:20 -0500

On Fri, Sep 19, 2025 at 12:50 AM Manuel Giraud <manuel <at> ledu-giraud.fr>
wrote:

>> When describing the behavior of 'backward-sentence', the manual states
>> that this command leaves point "just before the first character of the
>> sentence".  This is incorrect, as 'backward-sentence' actually leaves
>> point _on_ the first character of the sentence.

> Hi Eric,

Hi Manuel,

Thanks for your reply.

> I think that "just before" is also correct because the point of
> insertion *really is* just before the first character of the sentence.
> And IMO, in this regard, "just before" is more precise than "on the
> character".

You are correct.  I had been misunderstanding the term "point" to mean
"cursor", and somehow did not see this mistake when exploring this
(non-)issue.

>> When I first saw this, I thought I had to be missing something, but
>> after reading through adjacent docs to make sure I had the right
>> interpretation of point being "on" a character vs "before"/"after" it,
>> and then multi-checking that I wasn't simply misreading the manual, I
>> came to the conclusion that patching this description to use the word
>> "on" instead of the words "just before" would be worthwhile.

> Do you have example of such usage of "on"?

I didn't have any exact examples, but did have some pieces of
"supporting evidence", which are now irrelevant as such, since I was
reading them with the same misunderstanding as the manual text I was
trying to fix.  In case someone is interested though, one such piece
comes from the Elisp manual's description of 're-search-backward'
(which is used under the hood by 'backward-sentence'), which says
that:

     "This function searches backward in the current buffer for a
     string of text that is matched by the regular expression REGEXP,
     leaving point at the beginning of the first text found."

I had been interpreting the word "at" to be synonymous with "on", due
to my aforementioned misunderstanding of point vs cursor.

Sorry for the noise on this,
--
Eric Frederickson

Message #17 received at 79470 <at> debbugs.gnu.org (full text, mbox):

From: ERIC Frederickson <ericfrederickson68 <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 79470 <at> debbugs.gnu.org
Subject: Re: bug#79470: [PATCH] backward-sentence: Fix inaccuracy in manual's
 description
Date: Fri, 19 Sep 2025 13:20:37 -0500

On Fri, Sep 19, 2025 at 1:14 AM Eli Zaretskii <eliz <at> gnu.org> wrote:

>> When describing the behavior of 'backward-sentence', the manual
>> states that this command leaves point "just before the first
>> character of the sentence".  This is incorrect, as
>> 'backward-sentence' actually leaves point _on_ the first character
>> of the sentence.
>
> In Emacs, point cannot be _on_ a character, it is always _between_
> two characters.  The Emacs user manual says:
>
>      By default, the cursor in the selected window is drawn as a solid
>   block and appears to be _on_ a character, but you should think of
>   point as _between_ two characters; it is situated _before_ the
>   character under the cursor.  For example, if your text looks like
>   ‘frob’ with the cursor over the ‘b’, then point is between the ‘o’
>   and the ‘b’.  If you insert the character ‘!’ at that position,
>   the result is ‘fro!b’, with point between the ‘!’ and the ‘b’.
>   Thus, the cursor remains over the ‘b’, as before.

Understood.  Thanks for explaining.  I'm surprised that I wasn't aware
of this key difference between point and the cursor. I had thought
that point was simply a synonym for "cursor". Misunderstanding fixed.

> So you should understand the "before the first character" part of
> what the manual says in this context.
>
> So I don't think what the manual says is inaccurate.

Yes.  Apologies for the amateur mistake.

>> Also: I hope that I'm not cluttering the mailing list with too many
>> small patches sent close together.  I've happened to have a good
>> deal of free time this week and have been enjoying trying to make
>> some improvements to my favorite program.  If anything I've been
>> doing lately has been causing too much noise for anyone, please do
>> let me know what kind of conduct is best appreciated around here,
>> and I'll do my best to align with that.
>
> No problems here, feel free to submit any issue you think is worthy
> of discussing.

Sounds good.

Thanks for bearing with me on this thread,
--
Eric Frederickson

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