# [texhax] Error in argument of \section.

Robin Fairbairns Robin.Fairbairns at cl.cam.ac.uk
Wed Apr 27 10:25:38 CEST 2005

>       There may be an error in the \section command of Latex2e. I get an
> "Illegal parameter in the definition of..."  error message when I include the
> \overrightarrow command in the math mode in the argument of the \section command.
> Enclosing a stripped down version of an example. Could you please comment?

a simple consideration of probabilities would have led you to realise
that such an error was improbable.

as documented, when \section has no optional argument, the argument is
a moving one.  \overrightarrow is a fragile command.  fragile commands
regularly produce odd error messages in moving arguments.

\section{$\protect\overrightarrow{A}$}