template <typename T>
T string_to_number (const std::string &text, T def_value) {
    std::stringstream ss;
    for (std::string::const_iterator i = text.begin(); i != text.end(); ++i)
        if (isdigit(*i) || *i=='e' || *i=='-' || *i=='+' || *i=='.') ss << *i;
    T result;
    return ss >> result ? result : def_value;
}