FunctionalProgramming

Functional programming is an approach to the internal design of software characterized by:

• The reification of Routines as Values. In order to qualify as functional, a programming language must let you assign functions to variables, pass them as arguments to other functions, and return them from functions.
• Heavy use of pure Functions that operate on Immutable Data.
• Collocation of State and Process-external Effects near the top of the DependencyGraph.
• Use of algebraic identities, category theory, and other ideas from mathematics to prove that programs have certain desirable properties and that those properties are invariant under certain Refactorings.