3-line mathmode setting for upright indices wont work anymore

[Pratched]

I noticed, that this probably known "setting" for upright indices in mathmode without a need for single \mathrm{} every time, no longer works with tudscr. I havnt used tudscr for a while, but it worked at least 1-2 yrs ago.

\mathcode`\.="8000
\begingroup\lccode`~=`.
\lowercase{\endgroup\def~}#1{\mathrm{#1}}

Furthermore is it working when using scr itself or even article, as following MWE might prove.

\documentclass{tudscrbook}
%\documentclass{scrbook}
%\documentclass{article}
\mathcode`\.="8000
\begingroup\lccode`~=`.
\lowercase{\endgroup\def~}#1{\mathrm{#1}}
\begin{document}
$a_.b$\\
$a_.{bv}$\\
$a_b$
\end{document}

In case it is not as common as I thought, I cant remember where I first found this "setting", but it is described here as well.

[mrpiggi]

This is related to the usage of package mathastext in order to use Open Sans for math mode. The named package defines a large amount of tokens including . to be active.

I would suggest a slightly different approach for creating upright subscripts, inspired by https://tex.stackexchange.com/a/496613
With \uprightsubscripts and \italicsubscripts you can define, whether you want to use upright or italic subscripts as default. In order to get the contrary output, you only have to use $x_|subscript|$ instead of the normal syntax $x_{subscript}$.

\documentclass{tudscrartcl}

\makeatletter
\newcommand*\mathsub@upright[1]{\sb{\mathrm{#1}}}
\newcommand*\mathsub@italic[1]{\sb{\mathit{#1}}}
\newcommand*\mathsub@default{}
\newcommand*\mathsub@variant{}
\begingroup%
  \catcode`\_=13%
  \gdef_{%
    \kernel@ifnextchar(%)
      {\mathsub@variant}%
      {\mathsub@default}%
  }%
  \gdef_{\@ifnextchar|\mathsub@variant\mathsub@default}%
\endgroup%
\AtBeginDocument{%
  % default setting if \[upright|italic]subscripts wasn't invoked so far
  \ifx\mathsub@variant\@empty\italicsubscripts\fi%
  \mathcode`_="8000%
  \catcode`\_=12%
}
\newcommand*\uprightsubscripts{
  \let\mathsub@default\mathsub@upright%
  \def\mathsub@variant(##1){\mathsub@italic{##1}}%
  \def\mathsub@variant|##1|{\mathsub@italic{##1}}%
}
\newcommand*\italicsubscripts{%
  \let\mathsub@default\mathsub@italic%
  \def\mathsub@variant(##1){\mathsub@upright{##1}}%
  \def\mathsub@variant|##1|{\mathsub@upright{##1}}%
}
\makeatother


\begin{document}
$a_(b)$
$a_(bv)$
$a_|b|$
$a_|bv|$
$a_b$
$x_{default}$
$x_(variant)$
$x_|variant|$

\uprightsubscripts
$a_(b)$
$a_(bv)$
$a_|b|$
$a_|bv|$
$a_b$
$x_{default}$
$x_(variant)$
$x_|variant|$

\italicsubscripts
$a_(b)$
$a_(bv)$
$a_|b|$
$a_|bv|$
$a_b$
$x_{default}$
$x_(variant)$
$x_|variant|$
\end{document}

EDIT: Regarding #57 (comment), changed from $x_|variant|$ to $x_(variant)$

[keinstein]

Am 15.03.21 um 12:41 schrieb Falk Hanisch:

In order to get the contrary output, you only have to use `$x_|subscript|$` instead of the normal syntax `$x_{subscript}$`.

Why don't you suggest to use `[` and `]`? It is common LaTeX for optional arguments and has asymmetric borders.

[mrpiggi]

Well, the argument is not optional but a variant for the mandatory one. Nevertheless, asymmetric borders is a point, changed from $x_|variant|$ to $x_(variant)$

[Pratched]

Ah alright. Im not going to pretend, I fully understand whats been done neither in my original snippets or your solution, but many thanks.

[mrpiggi]

Leave open as potential feature for a future release

[Pratched]

That would be great. Especially since upright indices are expected most of the time throughout TUD.
One last question though, since Ive been too quick in closing anyway:

This does not seem to work when using predefined symbols with glossaries when using said syumbols with \gls{}? Might there be a quick fix for that as well?

[mrpiggi]

please open a new issue and provide a mwe

[mrpiggi]

According to https://tex.stackexchange.com/q/62705 and https://tex.stackexchange.com/q/245880 a slightly different and (hopefully) more robust solution considering text mode as well

\documentclass{tudscrartcl}
\usepackage[T1]{fontenc}

\makeatletter
\newcommand*\mathsub@upright[1]{\sb{\mathrm{#1}}}
\newcommand*\mathsub@italic[1]{\sb{\mathit{#1}}}
\newcommand*\mathsub@default{}
\newcommand*\mathsub@variant{}
\newcommand*\uprightsubscripts{
  \let\mathsub@default\mathsub@upright%
  \def\mathsub@variant(##1){\mathsub@italic{##1}}%
}
\newcommand*\italicsubscripts{%
  \let\mathsub@default\mathsub@italic%
  \def\mathsub@variant(##1){\mathsub@upright{##1}}%
}
\newcommand*\mathsub@choice{%
  \kernel@ifnextchar(%)
    {\mathsub@variant}%
    {\mathsub@default}%
}
\catcode`\_=\active%
\gdef_{\relax\ifmmode\expandafter\mathsub@choice\else\textunderscore\fi}%
\AtBeginDocument{%
  % ensure right catcodes
  \catcode`\_=\active%
  \mathcode`_="8000%
  % default setting if \[upright|italic]subscripts wasn't invoked so far
  \ifx\mathsub@variant\@empty\italicsubscripts\fi%
}
\makeatother

\usepackage{hyperref}
\begin{document}
\begin{figure}
  \caption{$x_y$}
  \label{z}
\end{figure}

bar_{foo}

bar_(foo)

$bar_{foo}$

$bar_(foo)$

\bigskip

$a_(b)$
$a_(bv)$
$a_b$
$x_{default}$
$x_(variant)$

\uprightsubscripts
$a_(b)$
$a_(bv)$
$a_b$
$x_{default}$
$x_(variant)$

\italicsubscripts
$a_(b)$
$a_(bv)$
$a_b$
$x_{default}$
$x_(variant)$
\end{document}

[mrpiggi]

Final solution can be found here: #58 (comment)