I learned F# in 2013 and had a lot of fun with it, some of that code remains on Github (e.g. a 2D platformer game for windows https://github.com/lihaoyi/FSharpMetro/tree/master/Applicati...).
My experience was that it was a surprisingly nice language with a surprisingly warty user experience: papercuts ranging from naming conventions and function call styles (`|> List.map` vs `.Select`), basic syntax (`foo.[0]` to lookup arrays), type system features (F# doesn't have covariance/contravariance even though C# does), IDE support (back then was only Visual Studio, whose support for F# was inferior to C#).
Ended up settling on Scala after that, as a language with its own Warts, but one that somehow managed to feel a more cohesive than F# did despite having largely the same featureset and positioning.
F# was my first functional language and one that changed how I look at programming, but at the same time I'm happy to not actually have to use it for serious programming!
F# supports both functional and OO call styles. That's why you have both `|> List.map` and `.Select`. It can be a bit confusing at first, but the interoperability with C# is worth it.
Array lookup in modern F# is just `foo[0]`.
Subtyping is much less common in F# than in C#, so the need for covariance/contravariance is correspondingly lower. Personally, I've never needed it.
F# support in Visual Studio is now excellent. You can also develop F# in VS Code.
FWIW I think writing F# is a really cohesive experience in day-to-day work. While there are usually at least two ways to do things, due to .NET interoperability requirements, it’s usually pretty clear which way is the “right” way to do something.
F# feels kind of similar to Python in this regard, where there might be more than one way to do it, but there is community and ecosystem consensus on what is the right way.
I think a lot of credit should go to Don Syme for this; he seems to have a very clear vision of what F# should and should not be, and the combination of features ends up being very tasteful and well composed.
I think these days F# is probably a big more polished than what you remember, so perhaps it's worth giving it another shot.
Being a hosted language always requires certain compromises (something that was also apparent in Scala). I used to do Scala professionally in its early days, but for me it felt it added just as much complexity as it addressed. I focused on Clojure back then (on the FP side at least), and I do think that F# probably brings more to the table than Scala. (if one is not constrained to Java, that is)
The tooling story is not great, but I've almost never seen great tooling for a language that's not super popular. I'm guessing what you get today with Rider is more or less as good as what VS has to offer.
Interesting - I'm curious where your thoughts are now on using FP/Scala in 2025?
I've always looked at F# with envy as it is a hosted ML that will have extremely battle tested bindings to the important day to day stuff via C# (Darklang's stories of struggling with postgres and AWS when using OCaml was a good cautionary tale on the risks of using less common langs as a startup)
Never had a chance to try out Scala but am a seasoned Clojurian, as an outsider it seemed Scala suffered a little from being not opinionated enough so the ML family has been more appealing to tinker with even though Scala supports type classes out the box and will also have great ecosystem support via the JVM
It's never been a better time to try Scala if you're interested in the FP side. It's still very much "not opinionated" but the community and ecosystem have benefited from a certain convergence and given up on the "better Java" front which is served by Kotlin more adequately. Of course you can still consume any Java library when needed but it's best to avoid it if possible. Today you can pick between several ecosystems:
- Typelevel libraries: modern and more welcoming take on ScalaZ ideas, rich and mature, extensible libraries that are written in "tagless final" style.
- ZIO: concrete "super monad" with 3 type parameters, shuns the Haskell baggage and category theory lingo but pretty much the same concepts, compile-time autowiring dependency injection, a bit less mature.
- Kyo: new effects system on the block, pushing Scala 3's type system to the limit to stack effects using an "auto-flattening" monad (sorry if I butchered the description).
- Li Haoyi's own ecosystem that sticks to the standard library and JVM built-in mechanisms whenever possible, focused on Python style expressiveness, only more functional and with stronger types.
- I'd skip Akka/Pekko libraries but it's still an interesting piece of software if you need actor based, stateful cluster sharding.
Martin Odersky and the LAMP are focused on "capabilities" and we should eventually see something like direct-style algebraic effects, or like Kyo but without monads.
Also we have much better build systems than before (Scala-CLI, Mill, sbt has improved a lot too), binary backwards compatibility since Scala 3, and a very capable LSP backend if you don't like IntelliJ IDEA.
So, there is a gazillion ways to do things and the community didn't settle on one? I don't find that very attractive when trying to learn a new language.
Very good summary, thank you! I've mostly stopped writing Scala, but it's still close to my heart.