# Is the blkarray package compatible with Xetex and amsmath?

Running xelatex on the file

\documentclass{article}
\usepackage{amsmath}
\usepackage{blkarray}
\begin{document}
\begin{blockarray}{c}
1
\end{blockarray}
\end{document}


gives the error

(/usr/local/texlive/2014/texmf-dist/tex/latex/blkarray/blkarray.sty)
(./test.aux)
! Incompatible list can't be unboxed.
<argument> \BA@first@box

l.9 \end{blockarray}


[Upon removing the reference to amsmath, the file compiles.]

Why does this error occur? Is it possible to use the blkarray package together with amsmath and xelatex?

Thank you.

• unrelated to xelatex, you get the same with (pdf)latex as well. Interesting. Who wrote that? – David Carlisle Feb 26 '15 at 19:58
• @DavidCarlisle: Some rabble-rouser. The documentation provides some form of life-long anonymity: "Warning! This style option is in the early stages of development." (dated 1999). The author seems to be listed as inactive. Sad that they just drop support like that, without notice... – Werner Feb 26 '15 at 20:11
• @Werner but note that 1999 date just refers to a change of email, the comment dates from 1992 – David Carlisle Feb 26 '15 at 20:27
• @DavidCarlisle: ...in true rabble-rouser fashion. – Werner Feb 26 '15 at 20:29
• I updated blkarray on ctan to fix this, first update this millennium:-) ctan.org/pkg/blkarray – David Carlisle Feb 28 '15 at 13:00

Nice MWE. It turns out amsmath tramples on box 0 (as it has a right to do, really) but it was unfortunate as blkarray was doing the same thing.

\documentclass{article}
\usepackage{array}\usepackage{amsmath}
\usepackage{blkarray}
\makeatletter
\newbox\BA@first@box
\makeatother
\begin{document}

\begin{blockarray}{c}
1
\end{blockarray}
\end{document}


You'll have no problem if you write your blockarray in math mode:

\documentclass{article}

\usepackage{blkarray}
\usepackage{mathtools}

\begin{document}

$\begin{blockarray}{[c\}} 1\\-1 \end{blockarray}$

\end{document}