With beamer, "Missing { inserted." (regression)

[Vincent Lefevre]

On 2022-02-17 19:17:38 +0100, Enrico Gregorio wrote:
> The syntax $e_\textnormal{m}$ has never been supported and
> if it works is just by accident. The proper syntax is to
> brace _any_ subscript (or superscript), but there’s usually 
> no problem when there is just a _single_ token.

In practice, people just see whether this works, without necessarily
thinking of other possibilities. Then the real issue is the change of
behavior by new versions.

I'm wondering... I can see, for instance:

texmf-dist/tex/latex/dvgloss/dvgloss.sty:\makeglshortcut[{[$_\textrm{\footnotesize#1}$\thinspace}
texmf-dist/tex/latex/nwejm/nwejmart.cls:    $_\mathsf{\arabic*}$
texmf-dist/tex/latex/unifith/unifith.cls:  \providecommand*{\rb}[1]{\ensuremath{_\mathrm{#1}}}

Isn't that similar?

> However, try $A_\notin$ and you’ll learn that $A_{\notin}$
> is much better.

This is a bit unfortunate. But I suppose that if this has never
worked, people would have added braces after seeing a failure.
This is not a big issue compared to incompatibilities introduced
in new TeX Live versions, potentially breaking many files.

-- 
Vincent Lefèvre <vincent at vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)