What is Functional Programming?

Functional programming is a programming style that treats computation as evaluating mathematical functions. Instead of changing data (mutating), you create new data. Think of it like math: f(x) = x + 1 doesn't change x, it produces a new value.

Core Principles:

• Pure functions: Same input always gives same output, no side effects
• Immutability: Don't modify data, create new versions
• First-class functions: Functions are values you can pass around
• Higher-order functions: Functions that take or return functions

Benefits:

• Predictable: Easier to reason about and test
• Parallelizable: No shared mutable state
• Composable: Build complex functions from simple ones
• Fewer bugs: Immutability prevents accidental changes

Common Patterns:

• Map: Transform each element
• Filter: Keep elements that match criteria
• Reduce: Combine elements into one value

FAQ

What languages support functional programming?

Pure functional: Haskell, Elm. Multi-paradigm: JavaScript, Python, Scala, F#, Clojure. Most modern languages have functional features.

Is functional programming better than OOP?

Neither is universally better. Functional is great for data transformations and avoiding bugs. OOP is great for modeling real-world entities.