string long_opt,

options_description* desc,

string help_text,

string help_group) {

if (desc) {

option_info oinf{move(help_text), 1};

(*desc)[help_group].insert(make_pair(make_pair(short_opt, long_opt), move(oinf)));

}

const char short_flag_arr[] = {'-', short_opt, '\0' };

const char* lhs_str = short_flag_arr;

string prefix = "--";

prefix += long_opt;

prefix += "=";

function<optional<string> (const string&)> kvp = [prefix](const string& input) -> optional<string> {

if (equal(begin(prefix), end(prefix), begin(input))) {

return input.substr(prefix.size());

}

else if (equal(begin(prefix) + 1, end(prefix), begin(input))) {

return input.substr(prefix.size() - 1);

}

return none;

};

vector<string> opts;

opts.push_back(lhs_str);

opts.push_back("--" + long_opt);

opts.push_back("-" + long_opt);

return {short_opt, long_opt, on<string, string>().when(_x1.in(opts)), on(kvp)};

string long_opt,

options_description* desc,

string help_text,

string help_group) {

if (desc) {

option_info oinf{help_text, 0};

(*desc)[help_group].insert(make_pair(make_pair(short_opt, long_opt), move(oinf)));

}

const char short_flag_arr[] = {'-', short_opt, '\0' };

vector<string> opt_strs = { short_flag_arr };

opt_strs.push_back("-" + long_opt);

opt_strs.push_back("--" + move(long_opt));

return on<string>().when(_x1.in(move(opt_strs)));

return [&out, desc] {

if (!desc) return;

if (desc->empty()) {

out << "please use '-h' or '--help' for a list "

"of available program options\n";

}

for (auto& opt_group : *desc) {

out << opt_group.first << ":\n";

for (auto& opt : opt_group.second) {

out << " ";

out << setw(40) << left;

ostringstream tmp;

auto& names = opt.first;

if (names.first != '\0') {

tmp << "-" << names.first;

for (size_t num = 1; num <= opt.second.num_args; ++num) {

tmp << " <arg" << num << ">";

}

tmp << " | ";

}

tmp << "--" << names.second;

if (opt.second.num_args > 0) {

tmp << "=<arg1>";

}

for (size_t num = 2; num <= opt.second.num_args; ++num) {

tmp << ", <arg" << num << ">";

}

out << tmp.str() << opt.second.help_text << "\n";

}

out << "\n";

}

};

ostream& out,

int exit_reason) {

auto fun = print_desc(desc, out);

return [=] {

fun();

exit(exit_reason);

};