Olyan rossz ez a magyarázat (nem definíció) rá?
Bár nem "funkcionális nyelvről" (azmiaz?) csak funkcionális programozásról, de itt a wiki bevezető szövege:
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 changing-state and mutable data. It is a declarative programming paradigm, which means programming is done with expressions or declarations[1] instead of statements. In functional code, the output value of a function depends only on the arguments that are passed to the function, so calling a function f twice with the same value for an argument x produces the same result f(x) each time; this is in contrast to procedures depending on a local or global state, which may produce different results at different times when called with the same arguments but a different program state. Eliminating side effects, i.e., changes in state that do not depend on the function inputs, can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming.
https://en.wikipedia.org/wiki/Functional_programming
A rust nem lisp vagy haskell, de az, hogy függvényeket írunk benne, szvsz bőven teljesíti amit a wiki ír a paradigmáról. Amúgy meg
It depends on what qualifies as a “functional programming language.” If by “functional” we mean purely functional, then no, but neither by that definition are OCaml, SML, or the various lisps. If by functional we mean supporting higher-order programming, then yes, but then so are Java, C#, and C++.
https://www.quora.com/Is-Rust-a-functional-programming-language