On Fri, May 6, 2011 at 22:33, Wolfgang Schuster wrote:

Am 06.05.2011 um 16:50 schrieb Mojca Miklavec:

...

Hello,

This is probably a very trivial question, but I'm not sure how TeX works in that respect. I'm used to use a macro   \def\unit#1{{\rm\ #1} in constructs such as $1\unit{cm^2} \times 2\unit{cm}$. However I figured out that the contents of \unit{} cannot be broken accross lines, most probably because this becomes an hbox.

Is there any simple workaround?

\def\unit{\groupedcommand{\rm\ }{}}

or

\def\unit#1{\bgroup\rm\ #1\egroup}

{ and } are same as \begingroup and \endgroup in math mode and prevent and a line break of the content.

Wow! Interesting. I never realized that {} prevents breaking in math mode. However, your solution to replace {} with \bgroup\rm \egroup works, but only if I replace it in the formula itself. If I change only the definition, it still won't break (maybe because I use a pair of braces already in \unit{cm+cm}). But at least now I know how to solve the problem. I can still use an explicit \rm instead of using \unit macro. Another question: how should I signal an allowed break in math mode? \penalty0 or is there some more sensible option? (\hskip doesn't seem to have any effect at all.) Thanks, Mojca