Xlop (eXtra Large OPeration) will typeset arithmetic problems
either in-line or "as in school" (using French school
conventions). So for example, \opadd{2}{3} can give either
$2+3=5$ or something similar to: \begin{tabular}{r} 2\\ +3\\
\hline 5\end{tabular}. Furthermore, numbers may be very large,
e.g 200 figures (with a very long compilation time). Many other
features allow to deal with numbers (tests, display, some high
level operations, etc.)
