Welcome back! Today, we'll master what we learned about backward compatibility in practice. Get ready to apply all the knowledge to practice tasks, but first, let's look at two examples and analyze them.

Suppose that initially, we have a complex data processing function designed to operate on a list of maps, applying a transformation that converts all string values within the maps to uppercase. Here's the initial version in C++:

To enhance this function, we'll introduce an overloaded function to allow custom transformation and filtering capabilities while maintaining backward compatibility.

Function templates in C++ allow you to write generic, reusable code that can handle different data types. By using templates, you define a blueprint for a function without specifying the exact data types the function will operate on. This allows the compiler to generate a version of the function with the correct data types when the function is called.

In the code snippet below, function templates are used to define a generic version of the process_data function. This templated function accepts custom transformation and filtering logic through lambda expressions, allowing for flexible processing while maintaining the function's default behavior to ensure backward compatibility.