Functional Programming

Definition

• "Key linguistic abstraction" of functional languages is the mathematical function.
• A function maps an input to an output; for the same input, it always produces the same output. Mathematical functions are stateless.
• Functions are first-class: can be used as input for functions, and produce functions as output.

Compared to Imperative

An Imperative Programming Language...

• Involves mutable state that changes throughout execution.
• Commands specify computations by destructively changing state.
• Procedures (or methods) have side effects that update state and produces a return value.