Functional Programming

Functional programming (FP) emphasizes pure functions, immutability, and higher-order functions.

Core Ideas

• Pure functions: no side effects, same output for same input.
• Immutability: prefer creating new values instead of mutating.
• Higher-order functions: functions that accept or return functions.

Examples (Python)

# map/filter/reduce
nums = [1, 2, 3]
doubled = list(map(lambda x: x*2, nums))
filtered = list(filter(lambda x: x % 2 == 1, nums))

When to Use FP

FP makes reasoning about code easier and is useful for parallelism, but sometimes imperative code is clearer for simple tasks.