Complex sentence: In computer science, functional programming is a programming paradigm, a style of building the structure and elements of computer programs, that emphasizes functions that produce results that depend only on their inputs and not on the program mutable state-i.e. pure mathematical functions.
Split into simpler sentences: In computer science, functional programming is a programming paradigm, a style of building the structure and elements of computer programs, that treats computation as the evaluation of mathematical functions and avoids state and mutable data. Functional programming emphasizes functions that produce results that depend only on their inputs and not on the program state-i.e. pure mathematical functions.