struct Point {
 double latitude;
 double longitude;
};
 
template <typename PropertyType, PropertyType Point::*property>
PropertyType get(const std::unordered_map<std::string, std::unique_ptr>& dict) {
   const auto &[it_min, it_max] = std::minmax_element(std::begin(dict), std::end(dict), [](const auto& p1, const auto& p2){
       return *(p1.second).*property < *(p2.second).*property;
   });
   return *(it_min->second).*property;
}

int main() {
   std::vector p;
   std::unordered_map<std::string, std::unique_ptr> dict;

   get<double, &Point::latitude>(dict);

   return 0;
}