# undefined control sequence - \@rllanguagename

I've been using LyX for a while for math typing. So far I was using the "standard article" class, and everything worked well. But when I'm trying to use an AMS article class, I get this error (even if the document is empty):

! Undefined control sequence.
\moreL ...dL \beginL \csname from\@rllanguagename
\endcsname
l.18 \begin{document}

The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., \hobx'), type I' and the correct
spelling (e.g., I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

! Undefined control sequence.
\moreL ...dL \beginL \csname from\@rllanguagename
\endcsname
l.18 \begin{document}

The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., \hobx'), type I' and the correct
spelling (e.g., I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

LaTeX Font Info:    Font shape HE8/cmr/m/n' will be
(Font)              scaled to size 10.0pt on input line 18.
(newfile1.aux) )


It also says this, few lines earlier:

Package babel Warning: No hyphenation patterns were preloaded for
(babel)                the language Hebrew' into the format.
(babel)                Please, configure your TeX system to add them and
(babel)                rebuild the format. Now I will use the patterns
(babel)                preloaded for english instead on input line 57.


This is the code that produces the problem (it happens also with an empty document):

\documentclass[oneside,english,hebrew]{amsart}
\usepackage[T1]{fontenc}
\usepackage[latin9,cp1255]{inputenc}
\usepackage{amsthm}

\makeatletter
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Textclass specific LaTeX commands.
\numberwithin{equation}{section}
\numberwithin{figure}{section}

\makeatother

\usepackage{babel}
\begin{document}
\selectlanguage{english}%
\inputencoding{latin9}hello\selectlanguage{hebrew}%

\end{document}


I'm using pdf(la)tex with LyX 2.1.3 on a Windows machine, Installed withe MiKTeX 2.9. Thanks.

• Please post a minimum working example of code that generates this error. Please also state which TeX engine -- pdf(la)tex, xe(la)tex, or lua(la)tex -- you use. – Mico Mar 2 '15 at 8:13
• The details are now in the question. Thank for the comment. – omrikap Mar 2 '15 at 8:25
• It seems to be a specific problem with amsart. – egreg Mar 2 '15 at 9:07
• Thanks. Is there another check I can do to say for sure? Can I get amsart from somewhere else? – omrikap Mar 2 '15 at 9:52
• amsart is doing some typesetting in the AtBeginDocument-hook when not every babel command has been set up. So it breaks when it encounters the @brackets command in \leftmarginii. Try \makeatletter\def\@rllanguagename{hebrew}\makeatother. – Ulrike Fischer Mar 2 '15 at 10:21

## 1 Answer

@Ulrike Fischer points out that

amsart is doing some typesetting in the AtBeginDocument-hook when not every babel command has been set up. So it breaks when it encounters the @brackets command in \leftmarginii. Try

\makeatletter
\def\@rllanguagename{hebrew}
\makeatother

• Since this answer entirely consists of a comment made by someone else, should it not be made Community Wiki? – Paul Gessler Jun 6 '15 at 21:48