# Overlays and verbatim

Another weird LaTeX problem. I have a piece of code on my slide and the result it gives. I want to change the code slightly and visualize the change in the result. Normally in LaTeX beamer slides, I would use overlays like this:

Query:
\begin{verbatim}
some code
\alt<2>{slightly changed code on slide 2}{original code on slide 1}
some more code
\end{verbatim}

Result:
this item is the same in both
\visible<1>{this one is only there for the original code}
\visible<2>{this one is only there for the changed code}


So far, so good. The code is in a verbatim environment, so I have cannot put the overlay around the line I want to change, but that’s fine, let’s make it an alternative around the whole verbatim part. But, unfortunately, the problem is that you cannot put a verbatim environment inside of overlays (learn why). So you have to hack it. This is the code I want, the line with FILTER is the one I only want to have on the second slide:

\begin{verbatim}
SELECT ?book ?author ?releasedate
WHERE {
?book dbo:author ?author .
{
?book dbp:releaseDate ?releasedate .
} UNION {
?book dbp:pubDate ?releasedate .
}
FILTER (?releasedate > 1950)
}
\end{verbatim}


Like in my post on using verbatim inside of verbatim, I have to end the verbatim environment prematurely, skip back over the space and then I can include the overlay inside of verb.

\begin{verbatim}
SELECT ?book ?author ?releasedate
WHERE {
?book dbo:author ?author .
{
?book dbp:releaseDate ?releasedate .
} UNION {
?book dbp:pubDate ?releasedate .
}
\end{verbatim}
\vspace{-0.5\baselineskip}
\verb|  |\visible<2>{\texttt{FILTER (?releasedate > 1950 )}}\\
\verb|}|
\\


Not the most elegant way, but it works…