"LaTeX3 Error: Command '\textsi' not yet defined!"

Guenter Milde milde at users.sf.net
Sun Feb 16 15:38:22 UTC 2020

On 2020-02-16, Richard Kimberly Heck wrote:
> On 2/15/20 5:52 PM, David Pesetsky wrote:
>> I was using Lyx for Mac rather extensively to write a long-ish
>> manuscript about a year ago, but have been away from it for a while.

>> In the interval, a problem has arisen, though nothing has changed in
>> my setup besides updating Lyx and Latex via TexLive.  I install the
>> embrac package, which ensures non-italic brackets in otherwise
>> italicized environments.  This used to work without a problem, but now
>> generates the error message:

>> LaTeX3 Error: Command '\textsi' not yet defined!

>> I am sure of my trouble-shooting, since commenting out the usepackage
>> command eliminates the error. 

Aside: It might also be a (new) incompapatibility with some other package
which would be solved by commenting out the other one...

> This is pretty suspicious. It suggests, to me, that LaTeX3 is being used
> to compile this file, which will almost certainly cause major problems
> with LyX. 

More probabely, one updated package (embrac, one of its dependencies or some
other) now uses the LaTeX3 syntax in LaTeX2e package (expl3.sty or so)
which generates the error. Looking at the first line(s) of the LaTeX log
will show the used LaTeX version.

> Then again, it's possible that the problem is just local to
> the embrac package. You might try writing the maintainer at
> contact at mychemistry.eu.

A minimal example would be helpfull there as well as here...


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