Functional Programming Languages
Functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions. Functional programming emphasizes the definition of functions rather than the implementation of state machines, in contrast to procedural programming, which emphasizes the execution of sequential commands. A purely functional program does not use mutation: rather than modifying state to produce values (as is done in imperative programming), it constructs new values from (but does not overwrite) existing values.
There is no uniform agreement on what constitutes functional programming or a functional programming language. Often considered important are first-class functions (including anonymous functions), closures, and recursion. Other common features of functional programming languages are continuations, Hindley-Milner type systems, non-strict evaluation (i.e. "laziness") or explicit suspensions, and monads.