It’s just like “normal” programming, but… you can’t modify variables… you can’t print… you can’t use mutable data structures. But no. Functional programming isn’t what it isn’t.

Another tenet of functional programming philosophy is not to modify data outside the function. In practice, this means to avoid modifying the input arguments to a function. Instead, the return ...

Functional programming relies on pure functions and avoids shared state and mutable data. It’s a programming style that rose to prominence with languages like Clojure, Scala, and Elm ...