What is the main idea of functional programming?

Functional programming is based on the idea of computation through the application of functions. Key principles:

• Pure functions: Functions without side effects. They always return the same result for the same inputs.
• Immutability of data: Variables do not change their value after initialization. Instead, new data is created.
• Functions as first-class objects: Functions can be passed as arguments, returned from other functions, and assigned to variables.
• Absence of mutable state: The program is built on computations rather than changing global or local state.

Example of a pure function:

// Pure addition function
def add(a, b):
    return a + b

// This function is not pure because it modifies an external variable
x = 0
def increment():
    global x
    x += 1

Advantages:

• Simplifies testing and debugging (due to the absence of side effects).
• Easier to parallelize computations.
• Increases code reliability.