Sample Tex File With Full Bidi Support (Including Numbers)

biditex-Sample.tex

\documentclass{article}
\usepackage{xepersian}
\makeatletter
% classes 1-3 are used in unicode-letters.tex, so we'll put the Latin letters in 4
\newcount\xp@n
\xp@n=`\A \loop \XeTeXcharclass \xp@n=4 \ifnum\xp@n<`\Z \advance\xp@n by 1 \repeat
\xp@n=`\a \loop \XeTeXcharclass \xp@n=4 \ifnum\xp@n<`\z \advance\xp@n by 1 \repeat
% this line would put Latin numbers in 4 class too.
\xp@n=`\0 \loop \XeTeXcharclass \xp@n=4 \ifnum\xp@n<`\9 \advance\xp@n by 1 \repeat
% when we encounter class 4, we'll do \startlatin
\XeTeXinterchartoks 0 4 {\startlatin}
\XeTeXinterchartoks 255 4 {\startlatin}
% and when we encounter class 0, we'll do \finishlatin
\XeTeXinterchartoks 255 0 {\finishlatin}
\XeTeXinterchartoks 4 0 {\finishlatin}
\newcommand{\startlatin}{\if@Latin\else\bgroup\beginL\latinfont\@Latintrue\fi}
\newcommand{\finishlatin}{\if@Latin\unskip\endL\egroup{ }\fi}
\makeatother
\XeTeXinterchartokenstate=1
\begin{document}
این یک آزمایش است
One Two Three
و ادامه آن
\end{document}

Original snippet are from this stackexchange answer:

http://tex.stackexchange.com/a/54325