Sets of mutually exclusive options in boost program options

Question

My program (prog.exe) supports the following four flags: -P, -p , -b and -s. However:

• -b and -p must be specified together, constitute a set, and have numeric values e.g. -b 42
• -s cannot be specified with the above set, and vice versa
• -P is mandatory in both cases

As such prog.exe can only be run as either

prog.exe -P -s 

or

prog.exe -P -b -42 -p 8

Is there a way to specify the above sets of mutually exclusive command line options in boost program options?

Roney

That's part of logic to implement in the (obligate) parseOptions() method of a boost::program_options client application IMHO. – Leopoldeen

I've come along such situations, and usually map them to some 'program execution mode' enum options. I first lookup option settings for this and after determining it, proceed with the specific options ... – Leopoldeen

Answer 1

You should start with a few tutorials [1][2] to understand how boost::program_options works.

Then, you can define two mutually exclusive options simply defining a small function as explained in real.cpp. For example, you can specify two conflicting (or depending) options defining a conflicting_options() function:

void conflicting_options(const boost::program_options::variables_map & vm,
                         const std::string & opt1, const std::string & opt2)
{
    if (vm.count(opt1) && !vm[opt1].defaulted() &&
        vm.count(opt2) && !vm[opt2].defaulted())
    {
        throw std::logic_error(std::string("Conflicting options '") +
                               opt1 + "' and '" + opt2 + "'.");
    }
}

and then calling

conflicting_options (vm, "quiet", "verbose");

right after boost::program_options::store()

I still don't understand if it's possible to define two mutually exclusive positional options, but that should be another question.

Gallup

In my opinion it is so much boilerplate code! Why wouldn't boost support mutually exclusive groups like python's argparse does it? – Huygens

Python is almost always more concise than C++, it's always been. C++11/14/17 are moving forward in this direction, but the pace is slow. – Gallup