I think it's because (I'm looking at Haskell in particular) there are a lot of great ideas implemented in them, but the purity makes writing practical or performant time-domain programs high friction. But you don't need both purity and the various tools they provide. You can use the tools without the pure-functions model.
In particular: My brain, my computing hardware, and my problems I solve with computers all feel like a better match for time-domain-focused programming.
My problem with functional languages is there never seems to be any easy way to start using them.
Haskell is a great example here. Last time I tried to learn it, going on the IRC channel or looking up books it was nothing but a flood of "Oh, don't do that, that's not a good way to do things." It seemed like nothing was really settled and everything was just a little broken.
I mean, Haskell has like what, 2, 3, 4? Major build systems and package repositories? It's a quagmire.
Lisp is also a huge train wreck that way. One does not simply "learn lisp" There's like 20+ different lisp like languages.
The one other thing I'd say is a problem that, especially for typed functional languages, they simply have too many capabilities and features which makes it hard to understand the whole language or how to fit it together. That isn't helped by the fact that some programmers love programming the type system rather than the language itself. Like, cool, my `SuperType` type alias can augment an integer or a record and knows how to add the string `two` to `one` to produce `three` but it's also an impossible to grok program crammed into 800 characters on one line.
> Lisp is also a huge train wreck that way. [...] There's like 20+ different lisp like languages.
Lisp is not a language, but a descriptor for a family of languages. Most Lisps are not functional in the modern sense either.
Similarly, there are functional C-like languages, but not all C-likes are functional, and "learn c-likes" is vague the same way "learn lisp" is.
You’re right and this is also a bit of a pet peeve of mine. “Lisp” hasn’t described a single language for more than forty years, but people still talk about it as if it were one.
Emacs lisp and Clojure are about as similar as Java and Rust. The shared heritage is apparent but the experience of actually using them is wildly different.
Btw, if someone wants to try a lisp that is quite functional in the modern sense (though not pure), Clojure is a great choice.
> I mean, Haskell has like what, 2, 3, 4? Major build systems and package repositories? It's a quagmire.
Don't know when was the last time you've used Haskell, but the ecosystem is mainly focused on Cabal as the build tool and Hackage as the official package repository. If you've used Rust:
- rustup -> ghcup - cargo -> cabal - crates.io -> hackage - rustc -> ghc
It's admittedly been years.
ghcup didn't exist, AFAIK. Cabal was around but I think there was a different ecosystem that was more popular at the time (Started with an S, scaffold? Scratch? I can't find it).