[XeTeX] odd dots in math when using russian for math

[Will Robertson]

On 2009-09-27 03:42:45 +0930, Imposeren <y at imposed.org.ua> said:

> when using "\SetSymbolFont{letters}{normal}{EU1}{\rmdefault}{m}{it}"
> 
> There appears one odd dot above commas and dots.
> 
> Are there any other ways to use russian in math?

I'd like to support Russian maths in unicode-math (as yet unreleased), 
but nothing exists at the moment. Here's a quick solution that might 
help to get you started:

\documentclass{article}
\usepackage{fontspec,expl3}
\setmainfont{Palatino Linotype}
\DeclareSymbolFont{cyrillic}{EU1}{\rmdefault}{m}{it}
\makeatletter\ExplSyntaxOn
\newcommand\XeTeXmathletter[2]{%
  \XeTeXmathcode #2="\mathchar at type\mathalpha \csname sym#1\endcsname #2\relax
}
\prg_stepwise_inline:nnnn {1024}{1}{1154}{
  \XeTeXmathletter{cyrillic}{#1}
}
\ExplSyntaxOff\makeatother
\begin{document}
Cyrillic letters: Б Д Ж\par
Cyrillic math: $  Б+Д+Ж $
\end{document}

In exchance for this help -- :) -- I hope you'll be able to tell me how 
Russian maths is usually typeset.
Are the Cyrillic letters always italic? Are any other symbols used 
besides the normal letters?

Many thanks,
Will