# Simple expression throws “Undefined control sequence”

I have a simple expression in my text which refuses to compile and I don't know why:

...\textit{isInterestedIn(Class$\<$? extends ContentChange$\>$ changeClass)}...

The complete error statement goes like this:

! Undefined control sequence.
l.298 ...? extends ContentChange$\>$ changeClass)}
mit einem der \textit{Tex...
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., \hobx'), type I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

I don't really understand, what's the problem here.

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What do you want. Type only $<$ and $y$. Or do you looking for something like: \langle\text{extends ContentChange}\rangle –  Marco Daniel Sep 1 '11 at 11:44

The command (called control sequence) \< is unknown. \ means the start of a control sequence. Write $<$ or $\backslash<$ instead, the latter if you really need a backslash .

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Thanks man, that did the trick for me. However, I'm a little curious why Texmaker returned me this expression from it's math character table...?! –  ubuntudroid Sep 1 '11 at 11:54
One can use \left< and \right> as abbreviations for \left\langle and \right\rangle; even \bigl< and \bigr> are legal. But \< has always been undefined in LaTeX (other than in the tabbing environment). –  egreg Sep 1 '11 at 12:56
-1 from me for suggesting $\backslah$ for text mode backslash. For obtaining a backslash in text mode, use \textbackslash; for using < and > in text mode, use T1 font encoding (or an opentype font). –  Aditya Sep 1 '11 at 18:13
@Aditya: thanks for explaining the downvote. You could add your comment as answer. Btw. I assume the backslash is not needed at all: See for example public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) here in Java documentation. And for deciding choosing math < or text < I don't see much information of the OP about the context such as encoding or desired shape of <, so I just fixed and explained. –  Stefan Kottwitz Sep 1 '11 at 19:21

You do not need to use math mode to get text < and >. A simpler solution is to either use T1 font encoding, or an opentype font (with lualatex or xetex). For example, with pdflatex

\documentclass{article}
\usepackage[T1]{fontenc}
\begin{document}
\textit{<text>}
\end{document}

or with lualatex

\documentclass{article}
\usepackage{fontenc}
\setmainfont{TeX Gyre Pagella}
\begin{document}
\textit{<text>}
\end{document}
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