Warm greetings! This lesson introduces data streams, which are essentially continuous datasets. Think of a weather station or a gaming application gathering data per second — both are generating data streams! We will master handling these data streams using C++, learning to access elements, slice segments, and even convert these streams into strings for easier handling.

In C++, data streams can be represented using vectors and maps from the STL (Standard Template Library). Let’s consider a straightforward C++ class named DataStream. This class encapsulates operations related to data streams in our program:

To use it, we create a sample data stream as an instance of our DataStream class, where each element is a map:

To look into individual elements of a data stream, we use indexing. The get() method we introduce below fetches the i+1-th element from the data stream:

Here, we can see the get() method in action:

In essence, stream.get(2) fetched us {"id": 3, "value": 300} — the third element (since indexing starts from 0). At the same time, stream.get(-1) fetches the last element, which is {"id": 4, "value": 400}.

The code snippet if (i < 0) { i += data.size(); } is particularly relevant here. It allows negative indexing by converting a negative index into the corresponding positive index, effectively letting -1 refer to the last element, -2 to the second last, and so on. This approach is useful for accessing elements from the end of the data stream efficiently.

Fetching a range of elements rather than a single one is facilitated by slicing. We introduce a slice() method to support slicing:

Here's a quick usage example:

For better readability, we may wish to convert our data streams into strings. To ensure the conversion works consistently, we will create a custom string representation for our data elements. Have a look at the to_string method in action:

To see it in action:

It prints: [{"id": 1, "value": 100}, {"id": 2, "value": 200}, {"id": 3, "value": 300}, {"id": 4, "value": 400}].

In this lesson, we've explored data streams, discovered how to represent and manipulate them using native C++ data structures, especially vectors and maps, and encapsulated operations on data streams with C++ classes.

Now it's time to apply your newfound knowledge in the practice exercises that follow!