Brief outline of the issue

With a recent (2024-06-01-ish) release of LaTeX, use of the bidi package in conjunction with the memoir class causes the @-expressions of longtable environments to be printed extraneously. It seems that using a \multicolumn command is necessary to trigger the bug.

According to the discussion at Issue latex3/latex2e#1368, this may be because the array package, whose definitions bidi redefines, was recently changed.

I can reproduce the problem only with memoir; the standard article and book classes seem to be unaffected.

Check/indicate

• Relevant to the xepersian package
• The bidi package issue tracker has been searched for similar issues?
• The xepersian package issue tracker has been searched for similar issues?
• Links to <tex.stackexchange.com> discussion if appropriate
• Links to <qa.parsilatex.com> discussion if appropriate

Minimal example showing the issue

\documentclass{memoir}
\usepackage{longtable}
\usepackage{bidi}
\begin{document}

\begin{longtable}{l}
\multicolumn{1}{c}{foo} \\
\end{longtable}

\begin{longtable}{r@{x}l@{x}r@{x}l@{x}r@{x}l}
a & b & c & d & e & f \\
\end{longtable}
\end{document}

Expected behavior

The second longtable environment should print something like the following:

axbxcxdxexf

Instead it prints the following:

axbxcxdxexf
x

Log and PDF files

test.log
test.pdf