[Boost-users] [Program Options] Requiring command-line options

Heya! I just thinking about switching from simpleOpt to BoostPO for command line handling, mainly because of its support of configuration files. This may be a stupid question, but I haven't seen anything about making a command line parameter *required*. You'd think this is a pretty common thing, but I didn't see any mention of it in the tutorials or anything. I guess I could just make certain parameters default -1/NULL or something, and then test at the end if they're still equal to that, but that seems a bit ugly. Is there built in support (a flag in the "add_options" function or something) for making certain parameters required? Thanks a lot!