Problem with \bordermatrix inside array

Question

When a \bordermatrix is placed inside an array, the spacing between rows will be wrong (see the MWE below). What is causing this problem? Is there a solution?

\documentclass{book}

\begin{document}

A simple matrix created with \verb+\bordermatrix+; right spacing between rows:
\[
  \bordermatrix{%
    & 1 & 2 \cr
    1 & x1 & x2 \cr
    2 & x3 & x4 \cr
    3 & x5 & x6}
\]

The same matrix inside an \texttt{array}; wrong spacing between rows:
\[
\begin{array}{c}
  \bordermatrix{%
    & 1 & 2 \cr
    1 & x1 & x2 \cr
    2 & x3 & x4 \cr
    3 & x5 & x6}
\end{array}
\]

\end{document}

Answer 1

This is caused because the \bordermatrix uses the \baselineskip for the spacing and array sets this to 0pt.

Restoring the value of \baselineskip in the cell fixes the issue:

\documentclass{book}

\begin{document}

\[
\edef\savedbaselineskip{\the\baselineskip\relax}
\begin{array}{c}
    {\baselineskip=\savedbaselineskip
    \bordermatrix{%
    & 1 & 2 \cr
    1 & x1 & x2 \cr
    2 & x3 & x4 \cr
    3 & x5 & x6}}
\end{array}
\]

\end{document}

This is done inside a group to keep the definition local.

Answer 2

An altenative way to restoring \baselineskip, which has been shown by Martin, is using \parbox or minipage for embedding the \bordermatrix, within the array. This would also restore the spacing.