line break inside cases environment

Question

I have an equation using a cases environment, with one case with a long description text:

\begin{eqnarray*}
    \begin{cases}
        1 \text{too long description of the first case,
            not fitting on the page}\\
        0 \text{shorter description}
    \end{cases}
\end{eqnarray*}

The text of the first case is cut of, as it is too long for my page width.

How can I let LaTeX split the line? Using a matrix does not seem like a clean solution to me...

Answer 1

You could use \parbox with top alignment:

\begin{equation*}
    \begin{cases}
        1 & \parbox[t]{.6\textwidth}{too long description of the first case,
            not fitting on the page}\\
        0 & \text{shorter description}
    \end{cases}
\end{equation*}

Further, better avoid the old eqnarray environment. Use align or another multi-line displayed math environment of amsmath. Here, even simply equation* or \[ ... \] would be sufficient, since it's a single line, and also doesn't need alignment. cases within is multi-line, but that doesn't matter for the outer environment.