Purely Functional Programming

Purely functional programming is a way of designing software where functions are treated as the main building blocks. These functions always produce the same output given the same input and do not have side effects, meaning they don't change anything outside their scope. This approach leads to more reliable, easier-to-understand code since it avoids issues like hidden changes or shared data. It's like working with mathematical functions that always give the same result, making programs more predictable, maintainable, and easier to test.