What are 3D game engines written in Haskell? I know F# has been used in some 3D visualization even though the language itself is quite young while Haskell has been around for ages. I’ve not heard from Epic or id or Crytek lead developers anything that would suggest they are willing to use any functional programming in a foreseeable future whatsoever.
That’s because there’s no point in doing that.
Big studio will use language of their codebase. When codebase has been used for 15 years or more, radical change, like language switch is the worst thing they could do.
Small studio or startup that is crazy enough to write their own engine will seek popular tools that have a lot of supported libraries.
I could understand desire to plug in common lisp or prolog into game engine, but there’s no point in going fully functional. Since you gain nothing or very little, it means pretty much nobody will try to do that.