GNU bug report logs - #26010
Indenting in tabulars and \&

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

From: Arash Esbati <arash <at> gnu.org>
To: auctex-bugs <bug-auctex <at> gnu.org>
Subject: Indenting in tabulars and \&
Date: Tue, 07 Mar 2017 14:24:15 +0100

Hi all,

please consider the following 2 examples and how they are filled: First
example works as expected, second one not because of \&:

--8<---------------cut here---------------start------------->8---
\documentclass{article}

\usepackage{longtable}

\begin{document}

Hit `C-c C-q C-e' inside env:
\begin{tabular}{ll}
  These lines will & appear \\
  at the end
  & of the table     
\end{tabular}
results in:
\begin{tabular}{ll}
  These lines will & appear \\
  at the end
                   & of the table
\end{tabular}

Hit `C-c C-q C-e' inside env:
\begin{tabular}{ll}
  These lines will appear \& 
  at the end \\
  of the &
  table
\end{tabular}
results in:
\begin{tabular}{ll}
  These lines will appear \& 
                             at the end \\
  of the &
           table
\end{tabular}

\end{document}
--8<---------------cut here---------------end--------------->8---

AUCTeX doesn't see the control symbol \&, it just takes the ampersand as
a column separator.  This issue is caused in the last part of the
function `LaTeX-indent-tabular':

--8<---------------cut here---------------start------------->8---
    (cond (...
	  (t
	   (+ 2
              (let ((any-col (save-excursion
                               (when (re-search-backward "\\\\\\\\\\|&" beg-pos t)
                                 (current-column)))))
                (if (and any-col (string= "&" (match-string 0)))
                    any-col
		  beg-col)))))))
--8<---------------cut here---------------end--------------->8---

I'm not aware of any way to fix this *only* by tweaking the regexp here:

    (re-search-backward "\\\\\\\\\\|&" beg-pos t)

Any idea?

Otherwise, I suggest the following change in `LaTeX-indent-tabular':

--8<---------------cut here---------------start------------->8---
    (cond (...
	  (t
	   (+ 2
              (let ((any-col (save-excursion
                               (when (re-search-backward "\\\\\\\\\\|[^\\]&" beg-pos t)
                                 (current-column)))))
                (if (and any-col (string= "&" (substring (match-string-no-properties 0) -1)))
                    (1+ any-col)
		  beg-col)))))))
--8<---------------cut here---------------end--------------->8---

Comments welcome.

Best, Arash

Message #8 received at 26010 <at> debbugs.gnu.org (full text, mbox):

From: Ikumi Keita <ikumi <at> ikumi.que.jp>
To: Arash Esbati <arash <at> gnu.org>
Cc: 26010 <at> debbugs.gnu.org
Subject: Re: bug#26010: Indenting in tabulars and \&
Date: Wed, 08 Mar 2017 02:49:41 +0900

Hi Arash,

> I'm not aware of any way to fix this *only* by tweaking the regexp here:

>     (re-search-backward "\\\\\\\\\\|&" beg-pos t)

> Any idea?

> Otherwise, I suggest the following change in `LaTeX-indent-tabular':
>     (cond (...
> 	  (t
> 	   (+ 2
>               (let ((any-col (save-excursion
>                                (when (re-search-backward "\\\\\\\\\\|[^\\]&" beg-pos t)
>                                  (current-column)))))
>                 (if (and any-col (string= "&" (substring (match-string-no-properties 0) -1)))
>                     (1+ any-col)
> 		  beg-col)))))))
> Comments welcome.

I think the form `(string= ...)' can be replaced with
`(= ?& (char-before (match-end 0)))'.

And here is another solution keeping the regexp untouched:
    (cond (...
	   (t
	    (+ 2
	       (let ((any-col (save-excursion
				(when (and
				       (re-search-backward "\\\\\\\\\\|&" beg-pos t)
				       (= ?& (char-after))
				       (not (TeX-escaped-p)))
				  (current-column)))))
		 (or any-col
		   beg-col))))))))

Using `TeX-escaped-p' might be overkilling since we allow loose usages of
(looking-at "\\\\\\\\") and (re-search-backward "\\\\\\\\... ) in this
function.

Bye,
Ikumi Keita

Message #11 received at 26010 <at> debbugs.gnu.org (full text, mbox):

From: Arash Esbati <arash <at> gnu.org>
To: Ikumi Keita <ikumi <at> ikumi.que.jp>
Cc: 26010 <at> debbugs.gnu.org
Subject: Re: bug#26010: Indenting in tabulars and \&
Date: Tue, 07 Mar 2017 20:27:46 +0100

Ikumi Keita <ikumi <at> ikumi.que.jp> writes:

>> Otherwise, I suggest the following change in `LaTeX-indent-tabular':
>>     (cond (...
>> 	  (t
>> 	   (+ 2
>>               (let ((any-col (save-excursion
>>                                (when (re-search-backward "\\\\\\\\\\|[^\\]&" beg-pos t)
>>                                  (current-column)))))
>>                 (if (and any-col (string= "&" (substring (match-string-no-properties 0) -1)))
>>                     (1+ any-col)
>> 		  beg-col)))))))
>> Comments welcome.

Hi Keita,

many thanks for checking and your response.

> I think the form `(string= ...)' can be replaced with
> `(= ?& (char-before (match-end 0)))'.

Yes, this is even more elegant.

> And here is another solution keeping the regexp untouched:
>     (cond (...
> 	   (t
> 	    (+ 2
> 	       (let ((any-col (save-excursion
> 				(when (and
> 				       (re-search-backward "\\\\\\\\\\|&" beg-pos t)
> 				       (= ?& (char-after))
> 				       (not (TeX-escaped-p)))
> 				  (current-column)))))
> 		 (or any-col
> 		   beg-col))))))))
>
> Using `TeX-escaped-p' might be overkilling since we allow loose usages of
> (looking-at "\\\\\\\\") and (re-search-backward "\\\\\\\\... ) in this
> function.

I agree, this seems overkill.  `[^\\]' is also used in
`LaTeX-hanging-ampersand-position' which is right above
`LaTeX-indent-tabular' in latex. el -- these functions would look more
in line with `[^\\]' in regexp.  This is the current suggestion:

  (cond (...
       (t
        (+ 2
            (let ((any-col (save-excursion
                             (when (re-search-backward "\\\\\\\\\\|[^\\]&" beg-pos t)
                               (current-column)))))
              (if (and any-col (= ?& (char-before (match-end 0)))
                  (1+ any-col)
               beg-col)))))))

Best, Arash

Message #14 received at 26010 <at> debbugs.gnu.org (full text, mbox):

From: Mosè Giordano <mose <at> gnu.org>
To: Arash Esbati <arash <at> gnu.org>
Cc: 26010 <at> debbugs.gnu.org
Subject: Re: bug#26010: Indenting in tabulars and \&
Date: Tue, 7 Mar 2017 21:26:50 +0100

Hi Arash,

2017-03-07 14:24 GMT+01:00 Arash Esbati <arash <at> gnu.org>:
> AUCTeX doesn't see the control symbol \&, it just takes the ampersand as
> a column separator.  This issue is caused in the last part of the
> function `LaTeX-indent-tabular':

Good catch.  I like the solution proposed by Keita, with or without
`TeX-escaped-p' (but I slightly prefer using these generic functions).
If you're going to install the fix, please add a test as well.

Bye,
Mosè

Message #19 received at 26010-close <at> debbugs.gnu.org (full text, mbox):

From: Arash Esbati <arash <at> gnu.org>
To: Mosè Giordano <mose <at> gnu.org>
Cc: 26010-close <at> debbugs.gnu.org
Subject: Re: bug#26010: Indenting in tabulars and \&
Date: Wed, 08 Mar 2017 11:45:24 +0100

Mosè Giordano <mose <at> gnu.org> writes:

> 2017-03-07 14:24 GMT+01:00 Arash Esbati <arash <at> gnu.org>:
>> AUCTeX doesn't see the control symbol \&, it just takes the ampersand as
>> a column separator.  This issue is caused in the last part of the
>> function `LaTeX-indent-tabular':
>
> Good catch.  I like the solution proposed by Keita, with or without
> `TeX-escaped-p' (but I slightly prefer using these generic functions).
> If you're going to install the fix, please add a test as well.

Hi Mosè,

thanks for your response.  I've installed a patch incl. a test; I went
for Keita's suggestion without `TeX-escaped-p', commit 991b582.  I close
this one then.

Best, Arash

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