source: downloads/boost_1_33_1/libs/program_options/example/custom_syntax.cpp @ 12

// Copyright Vladimir Prus 2002-2004.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt
// or copy at http://www.boost.org/LICENSE_1_0.txt)

/** This example shows how to support custom options syntax.

    It's possible to install 'custom_parser'. It will be invoked on all command 
    line tokens and can return name/value pair, or nothing. If it returns 
    nothing, usual processing will be done.
*/


#include <boost/program_options/options_description.hpp>
#include <boost/program_options/parsers.hpp>
#include <boost/program_options/variables_map.hpp>

using namespace boost::program_options;

#include <iostream>
using namespace std;

/*  This custom option parse function recognize gcc-style 
    option "-fbar" / "-fno-bar".
*/
pair<string, string> reg_foo(const string& s)
{
    if (s.find("-f") == 0) {
        if (s.substr(2, 3) == "no-")
            return make_pair(s.substr(5), string("false"));
        else
            return make_pair(s.substr(2), string("true"));
    } else {
        return make_pair(string(), string());
    }    
}

int main(int ac, char* av[])
{
    try {
        options_description desc("Allowed options");
        desc.add_options()
        ("help", "produce a help message")
        ("foo", value<string>(), "just an option")
        ;

        variables_map vm;
        store(command_line_parser(ac, av).options(desc).extra_parser(reg_foo)
              .run(), vm);

        if (vm.count("help")) {
            cout << desc;
            cout << "\nIn addition -ffoo and -fno-foo syntax are recognized.\n";
        }
        if (vm.count("foo")) {
            cout << "foo value with the value of " 
                 << vm["foo"].as<string>() << "\n";
        }
    }
    catch(exception& e) {
        cout << e.what() << "\n";
    }
}