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<head>
<title>UK TeX FAQ -- question label verbwithin</title>
</head><body>
<h3>Why doesn’t verbatim work within ...?</h3>
<p/>The LaTeX verbatim commands work by changing category codes. Knuth
says of this sort of thing “Some care is needed to get the timing
right...”, since once the category code has been assigned to a
character, it doesn’t change. So <code>\</code><code>verb</code> and
<code>\</code><code>begin{verbatim}</code> have to assume that they are getting the
first look at the parameter text; if they aren’t, TeX has already
assigned category codes so that the verbatim command doesn’t have a
chance. For example:
<blockquote>
<pre>
\verb+\error+
</pre>
</blockquote><p>
will work (typesetting ‘<code>\</code><code>error</code>’), but
<blockquote>
<pre>
\newcommand{\unbrace}[1]{#1}
\unbrace{\verb+\error+}
</pre>
</blockquote><p>
will not (it will attempt to execute <code>\</code><code>error</code>). Other errors one
may encounter are ‘<code>\</code><code>verb</code> ended by end of line’, or even the
rather more helpful ‘<code>\</code><code>verb</code> illegal in command argument’. The
same sorts of thing happen with <code>\</code><code>begin{verbatim}</code> ...
<code>\</code><code>end{verbatim}</code>:
<blockquote>
<pre>
\ifthenelse{\boolean{foo}}{%
\begin{verbatim}
foobar
\end{verbatim}
}{%
\begin{verbatim}
barfoo
\end{verbatim}
}
</pre>
</blockquote><p>
provokes errors like ‘File ended while scanning use of
<code>\</code><code>@xverbatim</code>’, as <code>\</code><code>begin{verbatim}</code> fails to see its
matching <code>\</code><code>end{verbatim}</code>.
<p/>This is why the LaTeX book insists that verbatim
commands must not appear in the argument of any other command; they
aren’t just fragile, they’re quite unusable in any command parameter,
regardless of <a href="FAQ-protect.html"><code>\</code><code>protect</code>ion</a>. (The <code>\</code><code>verb</code>
command tries hard to detect if you’re misusing it; unfortunately, it
can’t always do so, and the error message is therefore not a reliable
indication of problems.)
<p/>The first question to ask yourself is: “is <code>\</code><code>verb</code> actually
necessary?”.
<ul>
<li> If <code>\</code><code>texttt{<em>your text</em>}</code> produces the same result
as <code>\</code><code>verb</code><code>+<em>your text</em>+</code>, then there’s no need of
<code>\</code><code>verb</code> in the first place.
<li> If you’re using <code>\</code><code>verb</code> to typeset a URL or email
address or the like, then the <code>\</code><code>url</code> command from the
<i>url</i> will help: it doesn’t suffer from all the problems of
<code>\</code><code>verb</code>, though it’s still not robust;
”<a href="FAQ-setURL.html">typesetting URLs</a>” offers advice here.
<li> If you’re putting <code>\</code><code>verb</code> into the argument of a boxing
command (such as <code>\</code><code>fbox</code>), consider using the <code>lrbox</code>
environment:
<blockquote>
<pre>
\newsavebox{\mybox}
...
\begin{lrbox}{\mybox}
\verb!VerbatimStuff!
\end{lrbox}
\fbox{\usebox{\mybox}}
</pre>
</blockquote><p>
</ul>
<p/>Otherwise, there are three partial solutions to the problem.
<ul>
<li> Some packages have macros which are designed to be responsive
to verbatim text in their arguments. For example,
the <i>fancyvrb</i> package defines a command
<code>\</code><code>VerbatimFootnotes</code>, which redefines the <code>\</code><code>footnotetext</code> (and
hence the <code>\</code><code>footnote</code>) commands in such a way that you can include
<code>\</code><code>verb</code> commands in its argument. This approach could in
principle be extended to the arguments of other commands, but it can
clash with other packages: for example, <code>\</code><code>VerbatimFootnotes</code>
interacts poorly with the <code>para</code> option to the <i>footmisc</i>
package.
<p/> The <i>memoir</i> class defines its <code>\</code><code>footnote</code> command so that
it will accept verbatim in its arguments, without any supporting package.
<li> The <i>fancyvrb</i> package defines a command <code>\</code><code>SaveVerb</code>,
with a corresponding <code>\</code><code>UseVerb</code> command, that allow you to save
and then to reuse the content of its argument; for details of this
extremely powerful facility, see the package documentation.
<p/> Rather simpler is the <i>verbdef</i> package, which defines a
(robust) command which expands to the verbatim argument given.
<li> If you have a single character that is giving trouble (in
its absence you could simply use <code>\</code><code>texttt</code>), consider using
<code>\</code><code>string</code>. <code>\</code><code>texttt{my<code>\</code><code>string</code>_name}</code>
typesets the same as
<code>\verb+my_name+</code>, and will work in the argument of a command. It
won’t, however, work in a moving argument, and no amount of
<a href="FAQ-protect.html"><code>\</code><code>protect</code>ion</a> will make it work in
such a case.
<p/> A robust alternative is:
<blockquote>
<pre>
\chardef\us=`\_
...
\section{... \texttt{my\us name}}
</pre>
</blockquote><p>
Such a definition is ‘naturally’ robust; the construction
“<<i>back-tick</i>><code>\</code><code><<i>char</code></i>>” may be used for any
troublesome character (though it’s plainly not necessary for things
like percent signs for which (La)TeX already provides
robust macros).
</ul>
Documentation of both <i>url</i> and <i>verbdef</i> is in the
package files.
<dl>
<dt><tt><i>fancyvrb.sty</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/fancyvrb.zip">macros/latex/contrib/fancyvrb</a> (<a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/fancyvrb.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/macros/latex/contrib/fancyvrb/">browse</a>)
<dt><tt><i>memoir.cls</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/memoir.zip">macros/latex/contrib/memoir</a> (<a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/memoir.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/macros/latex/contrib/memoir/">browse</a>)
<dt><tt><i>url.sty</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/misc/url.sty">macros/latex/contrib/misc/url.sty</a>
<dt><tt><i>verbdef.sty</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/misc/verbdef.sty">macros/latex/contrib/misc/verbdef.sty</a>
</dl>
<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=verbwithin">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=verbwithin</a>
</body>
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