Why does combining arrays and \left/\right cause alignment?

Question

The following MWE is rendered as shown below:

\documentclass{article}

\begin{document}
\begin{array}[t]{@{}l@{}}
  \left[\int abc\right]\\
  \left[abc\right]
\end{array}
\end{document}

Why aren't the left brackets aligned? Removing the \int fixes it, but why? Is there a way to fix the alignment? (My real example involves nested arrays instead of an integral, but this was the simplest I could get).

Answer 1

The cause seems to be different size of brackets. For your (simple) case try the following:

\documentclass{article}

\begin{document}
\[
\begin{array}{@{}l@{}}
  \left[\int abc\right]\\
  \left[\strut abc\right]
\end{array}
\]
\end{document}

Alternative solution is use \bigl[ ...\bigr] instead left[ ...\right]. With this you will achieve equal big brackets:

\documentclass{article}

\begin{document}
\[
\begin{array}{@{}l@{}}
  \bigl[\int abc\bigr]\\
  \bigl[ abc\bigr]
\end{array}
\]
\end{document}