How to properly use ROS service

edit

Right now, I got some array of geometry_msgs::Point (geometry_msgs::Point[]) by C++. Now I want to use some clustering algorithm implemented in python. I think ros service might be a good choice for different programming language communication, So I have included the clustering algorithm in the ROS server.

I am confused by the client node. I don't want to have a main function since I cannot save the result for later. Instead, I want to have a regular c++ function which the input parameters are the data (geometry_msgs::Point[]) and the return is results from clustering node.

Is there a proper way to do this? or any other options?

For example:

// e.g. return the clustering center for the data, this is the function I would like to write
std::vector<geometry_msgs::Point> functionUseClusterServer(std::vector<geometry_msgs::Point> data){
    // call ROS server written by python
    ...
    return result_from_server;
    }

// I want that the functionUseClusterServer can be used in the main: 
int main(int argc, chat** argv){
    ...
    result = functionUseClusterServer(data);
    something_else = otherFunction(result);
    ...
{