When printing the "usage" of an application, should it be done on stdout or on stderr? Depending on the application I've seen several cases, but there doesn't seem to be one rule. Maybe I'm mistak...

If you take a look at the Combinatorica package in Mathematica8 in (mathematicapath)/AddOns/LegacyPackages/DiscreteMath/Combinatorica.m you will find the definitions of functions. What I'm interest...