# Functional Programming
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

Functional Programming (FP) treats computation as evaluation of mathematical functions, avoiding changing state and mutable data. Core concepts: pure functions (same input → same output, no side effects), immutability, higher-order functions, recursion, function composition. Languages: Haskell, Clojure, Elixir, Scala, JavaScript (FP-style).

## Core Explanation

Pure functions: no side effects → easier to test, reason about, parallelize. Map/Filter/Reduce: transform collections without loops. Currying: f(a,b) → f(a)(b). Monads (Haskell): handle side effects (IO, State, Maybe) in pure FP. FP influences: React (immutable state), Redux (pure reducers), Rust (pattern matching, iterators).

## Further Reading

- [Structure and Interpretation of Computer Programs (SICP)](undefined)