Marshall Clow wrote:
The simplest way for this to work is to define a single bool option "rtti". Then, use custom parsers to translate "frtti" and "fno_rtti" to "rtti=off" and "rtti=on" respectively. See http://boost.org/doc/html/program_options/howto.html#id2715843 which discusses exactly this "no" prefix handling. As a side effect users will be able to specity "--rtti=on", but maybe that's not a big problem.
Ok - I can see how that works, but I think I chose a bad example. Here's a different one:
My program has three reporting "modes": Normal -- print out some stuff Quiet -- print nothing Verbose -- print lots of stuff.
I need to respond to switches like "--quiet" and "--verbose", which is fine, but I more than one of them in the same command line is an error.
I can certainly check in my code to see if more than one was presented (and I will do that); I am just surprised that this functionality is not part of the program-options library.
Maybe in a future version. ;-)
Maybe. If you look at libs/program_options/example/real.cpp you'll see that I expected conflicting options to be handled by defining a function 'conflicting_options' and using it as appropriate. That still seems a good interface for me. Say: conflicting_options(vm, "normal", "quiet", "verbose"); is not worse IMO then: desc.conflicting_options() ("normal", "quiet", "verbose"); or any other syntax I can invent. It might be reasonable to expect such "conflicting_option" function to be part of library, though. - Volodya