What are the main advantages and potential disadvantages of using functional programming?

Functional programming (FP) is based on the use of pure functions, immutable data, and the absence of side effects.

Advantages:

• Ease of testing and debugging: pure functions always return the same result for the same inputs.
• Parallelism: lack of state makes parallel execution of code easier.
• Increased readability and modularity: functions are easy to compose and reuse.
• Predictability: absence of side effects reduces the number of errors.

Disadvantages:

• Performance: creating new objects instead of modifying existing ones can be more memory and time-consuming.
• Steep learning curve: unfamiliar style for developers accustomed to imperative programming.
• Limitations in some tasks: for example, complex state management or input-output requires special approaches (monads, effects).

Example in Python (a function without side effects):

def square(x):
    return x * x

print(square(5))  # always 25

Unlike this, imperative code can modify external state, which complicates understanding and testing.