\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> f = sin(x)/x;
> g = cos(y)-1;
Warning: the identifier "y" is neither assigned to, nor bound to a library funct
ion nor external procedure, nor equal to the current free variable.
Will interpret "y" as "x".
> g;
cos(x) - 1
\end{Verbatim}
\end{minipage}\end{center}
