Overloading operator << for containers

Today, I saw a line of code in one of our cpp files, it looks like this:
marshaller << obj_list;
what interesting is that obj_list is an instance of type std::vector, and one of my colleagues asked me if he can do similar things with an instance of type std::map<>.

The answer is "I don't know", because it depends on if the operator << is overloaded for the marshaller type for std::map<>.

The secret why "marshaller << obj_list;" works is that, the marshaller type has an overloaded operator << for std::vector. Something looks like this, assuming marshaller has type T:
T  &operator << (T &t, const vector avector){...}

Here is an example with cout:
ostream &operator << (ostream &out, const vector avector)
{
    vector ::const_iterator itr = avector.begin();
    for (; itr != avector.end(); ++itr)
    {
        out << (*itr);
    }
}

int main(void)
{
    vector str_vector;
    for (int i = 0; i < 10; i++)
    {
        stringstream str_stream;
        str_stream << i;
        str_vector.push_back(str_stream.str());
    }
    cout << str_vector;
}
The output is:
0123456789

So for this works with std::map<>, we need to overload << for std::map<>. 

Finally, it turned out that there is no such an overload, unfortunately. So we have to do it for each pare in the map.

Do It in a Programmer's Way

DiPw, I'd like to pronounce it like "deepyou", is my preferred way of doing things, especially things related with my job as a programmer/developer.

Recently, I was assigned a job to migrate documents from the old system to the new one, and this is to be done for each of our customers. In order to secure the migration, I need to check many configurations on both systems, they need to be similarly configured so the migration is transparent for the customers, ideally. What complicates things is also we have test systems and production systems, and the migration need to be done first on test systems then on production systems. So as a result, I have a lot of things to check and compare. Even worse, the settings are managed by several GUI applications so I have to click many times to find one setting on the old system then, do it on a different GUI on the new system. That is not only boring but also fault prone.

A colleague of mine kindly told me that the content of the GUI applications are finally stored in the database and he also gave me some SQL to retrieve the values. That is a big help, however, I still have to manage two types of databases, Oracle and SqlLite.

Why I have to do it manually? It's time consuming and error prone. Why not write a program doing all of these jobs for me? With always DiPw in head, I decided to write a Python program doing these boring jobs and finally it took me one day. Voila, now with the program, I retrieve all need information on all systems for a given customer in 20 minutes and when needed, I can retrieve most up-to-date information whenever I want in 20 minutes, this is impossible without the program. And when it comes the time to migrate another customer, I just run the program for this customer.

Well, I admit that the job is not all about getting all the settings, but it is the most boring part, so let a program do it!