The opposite of imperative is declarative, and the opposite of (pure) functional is non (pure) functional.
Schema and (to my limited knowldge) the ML family are in fact non (pure) functional. However, they share more functional-aspects with pure functional languages than most other popular languages do.
> Even Haskell has unsafePerformIO, which it might sadly need.
Sure, it's almost never a black and white thing. But I think for the sake of the argument we can call Haskell a pure functional language, even if it is indeed possible to write non pure functional code in it. There are actual pure functional languages (like Idris) but I think for practical use in the discussion it's fine to call Haskell pure functional. Scheme and ML languages are very different from Haskell though, so I think they deserve to be called differently. They are however also different from, say, C. So to improve our communication I think it is worth to not put those 3 things into 2 boxes. We need 3 boxes here.
Disclaimer: I want to emphasize that none of any of that says that a language is inherentially better or worse! This is just terminology-talk.
Functional does not mean just pure functional. And a purely pure functional language would literally be worthless as it wouldn't be able to do anything useful.
Maybe those examples are "most shining" from your perspective or definition but not mine. Mind to mention the specific languages?
That being said, to be precise, functional programming is a technique or style, it's not a property of a language anyhow. However, some languages make it very hard or even impossible to apply the style, either fully or partially. So practically speaking, that is how I classify a language as more or less functional.
> Functional does not mean just pure functional.
Yes, that's exactly what I said in my first sentence no?
Originally "functional programming" had the meaning of what we nowadays often call "pure functional programming" though. Language and definitions change over time. I was ranting a bit that the term "functional" is nowadays so unclear that there is little benefit in knowing that a language is "functional".
> And a purely pure functional language would literally be worthless as it wouldn't be able to do anything useful.
This is wrong. You haven't understand what functional programming is. In a nutshell it means that you are not directly executing effects, but rather that you build up a datastructure that describes the effect-execution. You then pass around an modify that datastructure to the point where you return it as the last thing that your does in the main-method (or whatever your language/runtime calls that). From that point on, this datastructure is being processed and the effects (like writing to a file, showing something on the screen) are (most likely) executed by the runtime.
In other words, there is no restrictions on what you can do with a pure functional language. You can try it out with Idris, which is a 100% pure functional language without any escape hatches. And still you can make it do all kinds of effectful things like processing files, sending emails, ...
> You haven't understand what functional programming is.
I almost exclusively use functional languages, so I'm not sure about that.
> I was ranting a bit that the term "functional" is nowadays so unclear that there is little benefit in knowing that a language is "functional".
I'm actually not sure that is a problem. Any examples? And it's quite common to describe something as "functional-first" if it has a functional core but allows other paradigms such as imperative or OOP, such as OCaml.
And a lot of this is based upon the semantics and definitions of the words like "pure", "functional", etc. which are more like spectrums than binary.
