runtime template mode processor, C++ (gcc)

runtime template mode processor

//g++  5.4.0

#include <iostream>

#include <boost/algorithm/string.hpp>
#include <boost/program_options.hpp>

namespace po = boost::program_options;

template<int N> class Processor{
public:
    std::string operator()(std::string&& s) const
    {
        return Processor<N & (N-1)>()(Processor<N & ~(N-1)>()(s));
    }
};

template<> class Processor<0>{
public:
    std::string operator()(std::string&& s) const
    {
        return s;
    }
};

enum Modes
{
    md_tolower = 1,
    md_toupper = 2,
    md_capitalize = 4,
    md_trim_start = 8,
    md_trim_end = 16,
    md_normalize_spaces = 32,
    md_stem = 64,
    md_sort = 128,    
};

template<> class Processor<md_tolower>{
public:
    std::string operator()(std::string&& s) const
    {
        boost::to_lower(s);
        return s;
    }
};

template<> class Processor<md_toupper>{
public:
    std::string operator()(std::string&& s) const
    {
        boost::to_upper(s);
        return s;
    }
};

template<> class Processor<md_capitalize>{
public:
    std::string operator()(std::string&& s) const
    {
        return s;
    }
};

template<> class Processor<md_trim_start>{
public:
    std::string operator()(std::string&& s) const
    {
        return s; // STUB
    }
};

template<> class Processor<md_trim_end>{
public:
    std::string operator()(std::string&& s) const
    {
        return s; // STUB
    }
};

template<> class Processor<md_normalize_spaces>{
public:
    std::string operator()(std::string&& s) const
    {
        return s; // STUB
    }
};

template<> class Processor<md_stem>{
public:
    std::string operator()(std::string&& s) const
    {
        return s; // STUB
    }
};

template<> class Processor<md_sort>{
public:
    std::string operator()(std::string&& s) const
    {
        return s; // STUB
    }
};

std::string apply(int mode, std::string&& value){
    // TODO
    return value;
}

int main(int argc, char** argv)
{
    int mode = 0;
    std::string value;
    
    po::options_description config_option_list("config options");
	config_option_list.add_options()
		("mode", po::value<int>(&mode)->default_value(0), "")
        ("value", po::value<std::string>(&value)->default_value(""), "")
    ;
    
	po::options_description option_list;
	option_list.add(config_option_list);
    
	po::command_line_parser parser(argc, argv);
	parser.options(option_list);
	
	po::variables_map option_values;
	po::store(parser.run(), option_values);
	po::notify(option_values);
    
    std::cout << apply(mode, std::move(value)) << std::endl;

}


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