Functional Programming (FP)
A programming paradigm where programs are constructed by applying and composing functions.
Functional Programming (FP) is a paradigm where programs are constructed by applying and composing functions. Functions are first-class citizens—passed as arguments, returned from functions, stored in variables.
Core principles:
1. Pure Functions: Same input always produces same output, no side effects
2. Immutability: Data never changes after creation
3. First-Class Functions: Functions are values
4. Higher-Order Functions: Functions taking or returning functions
5. Recursion: Preferred over loops
graph LR
Center["Functional Programming (FP)"]:::main
Rel_object_oriented_programming["object-oriented-programming"]:::related -.-> Center
click Rel_object_oriented_programming "/terms/object-oriented-programming"
Rel_procedural_programming["procedural-programming"]:::related -.-> Center
click Rel_procedural_programming "/terms/procedural-programming"
Rel_agile_methodology["agile-methodology"]:::related -.-> Center
click Rel_agile_methodology "/terms/agile-methodology"
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🧠 Knowledge Check
🧒 Explain Like I'm 5
Imagine a math [function](/en/terms/function) like f(x) = x + 2. You put in 3, you always get 5. Functional programming means your code works like math—reliable, no surprises, and you can combine simple functions to build complex ones!
🤓 Expert Deep Dive
Core concepts include immutability, first-class functions, higher-order functions, and lazy evaluation. Popular in systems requiring high concurrency and reliability (e.g., Haskell, Elixir, or JS with libraries like Ramda).