Functional Programming

Definitions

1. Functional programming (FP) is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids mutable state and side effects. Core principles include pure functions (same inputs always produce the same output), immutability (data is never modified in place), first-class functions (functions can be passed as arguments and returned as values), and higher-order functions (functions that operate on other functions, like map, filter, and reduce). FP makes code easier to reason about, test, and parallelize because functions without side effects can run independently. Languages like Haskell, Erlang, and Clojure are built around FP principles, while JavaScript, Python, Scala, and Rust support functional styles alongside other paradigms.

   In plain English: Functional Programming is a practical idea developers use to keep software understandable, easier to change, and more reliable as the codebase gets larger.

   Example: "We used Functional Programming in this code path so the behavior stays consistent across the project, new contributors can follow the intent quickly, and the team can change implementation details without turning routine maintenance into a risky rewrite."

Related Terms

• Curried Function
• Durable Function
• Factory Function
• First-Class Function
• Free Function
• Function Composition
• Function Overloading
• Function Pointer