boost regex formatter, how to use a custom function

Question

Well how do I invoke a custom formatting function when calling boost::regex_replace?

My code is as following:

template <typename T>
std::string fmt(boost::match_results<T> match) {
    auto str = match[1];
    if (str == ".") {
        return "\".\"";
    } else {
        return str;
    }
}
void __ConvertEscapeChar(std::string& action, std::string regex) {
    boost::regex re(regex);
    action = boost::regex_replace(action, re, &fmt, boost::regex_constants::match_all);
}

however it shows an error, "could not deduce template argument for __fmt". - Well what IS T actually?

Answer 1

Unless you need the flexibility of using a template in your fmt function for some reason that isn't obvious here, try this instead:

std::string fmt(boost::smatch match)