> Another is that in a pure language, you can look at a function and know for a fact that nothing you're seeing can ever be mutated. This eliminates a massive s

> Another is that in a pure language, you can look at a function and know for a fact that nothing you're seeing can ever be mutated. This eliminates a massive source of cognitive load when trying to read and understand code, as well as eliminating all sorts of bugs related to the program being in the wrong state. If you're trying to write functional code in a language not designed for it, you're missing out on those benefits. When you write functional code in imperative languages, these constraints aren't enforced by language, but they should be enforced by convention and code review.