OptionParseResult result;

result.is_long_option = false;

if (!arg.empty() && arg[0] == '-') {

result.prefix.append(1, '-');

if (arg.length() > 1 && arg[1] == '-') {

// long option

result.prefix.append(1, '-');

result.is_long_option = true;

auto first = arg.begin() + 2;

for (auto it = first, end = arg.end(); it != end; ++it) {

char c = *it;

if (c == '=' || c == ':') {

result.options.push_back(S(first, it));

result.values.push_back(S(it + 1, end));

break;

}

}

if (result.options.empty()) {

// didn't find value; use whole arg as option

result.options.push_back(S(first, arg.end()));

}

} else {

// short option

for (auto it = arg.begin() + 1, end = arg.end(); it != end; ++it) {

char c = *it;

if (c == '=' || c == ':') {

result.values.push_back(S(it + 1, end));

break;

} else {

result.options.push_back(S(1, c));

}

}

}

} // else not an option

return result;