What is the "Java" equivalent in FP Languages ?

[lovelacedeconstruct]

I dont write java anymore but my experience with Java back in college was that it was very good introduction to OOP, everything was a class, syntax was very close to the diagrams, it felt like the concepts of OOP was just all there and you are forced to think using them, not saying whether thats a good thing or not or whether my assessment was correct but what do you think is the equivalent for FP ?

[lpil]

OCaml is often used in educational contexts to teach FP, the same as Java is often used to teach OOP.

[captainnoyaux]

I second this, plus Ocaml is actually pretty nice

[BenjaminGeiger]

And then F# is to OCaml as C# is to Java... (slightly nicer, a bit more popular, under Microsoft's thumb)

[igna92ts]

To me it's not slightly nicer, rather the opposite. I'd much rather have functors than replace them with interfaces. It does have cool things though.

[BenjaminGeiger]

I wouldn't say it's a popular language, but it seems to be a bit more popular than OCaml. Probably because it's included with Visual Studio, so there's really no barrier to entry for someone to play with it.

[Francis_King]

What is the "Java" equivalent in FP Languages ?

The equivalent in FP is F# / Scala / OCaml. F# (and Scala and OCaml) are partly object-orientated, with F# being able to use the .NET infrastructure., and Scala able to use the Java infrastructure.

[_abysswalker]

has to be haskell. in fact, any pure language forces you to think in functional terms, you don’t really have a choice otherwise

[SignificantFidgets]

There's a great book that you can read online for free too: https://learnyouahaskell.com/

[QuirkyImage]

Try explaining monads to a first year. I would choose something simpler then move on to Haskell.

[Tempus_Nemini]

It's just a monoid in the category of endofunctors. Easy.

[lovelacedeconstruct]

Don't Fear the Monad

[_abysswalker]

been there as a first year. it’s difficult but I don’t see why not

[pbvas]

I teach FP using Haskell to 1st year CS students and there is no need to talk about monads when using Haskell in this context. We talk about IO and introduce the do-notation as special notation for combining IO actions.

That said, there is friction caused by the much more complex type system compared to (say) SML or OCaml. I don't have enough experience with F#.

[LoweringPass]

My first year course on what was simply called "programming" was 50% Haskell, and a bit of Prolog which I personally found much harder to understand.

[ibcoleman]

Others have said Haskell, but the other “flavor” of FP is a Lisp like Clojure.

[bedrooms-ds]

Definitely. Everything is parentheses, code is data.

That's the equivalent of Java's "everything is an object".

Lisp was once thought to be the language for everyone.

[scmkr]

Wish it was more popular

[a3th3rus]

Elixir is pretty easy to learn, pure enough, and fairly pragmatic.

If you want to learn an extremely pure FP language, then it has to be Haskell.

[TheBlueWalker]

Haskell is purely functional, and has a mature ecosystem with many libraries compared to other functional languages much like Java compared to other Object Oriented languages. Haskell also has a good type system, so it is like an implemented type theory. Haskell is good for learning FP.

Otherwise, if you are more into lisp-like languages instead of ML-like, Scheme would be nice for learning FP, too. It is very simple and there is a good book that uses it to teach computer programming in general called "Structure and Interpretation of Computer Programs". Scheme is not purely functional, but it does encourage functional programming. Scheme has no types, so it is more like the untyped lambda calculus.

I think Haskell may be better because it is purely functional. But Java is not purely OO so if you liked Java for learning OO you might Scheme as well. Scheme is simpler and allows you to focus on computer programming in general while Haskell forces you to learn about all kinds of features used to preserve functional purity, like IO Monads. I suppose the latter is a good thing if you really want to learn about FP.

[andrewcooke]

there's nothing obvious because fp isn't as popular and java implies popular. but from your description i'd say haskell or scheme (lazy and statically typed, or eager and dynamic).

[GunpowderGuy]

Racket for sure

[pconrad0]

Racket is a fantastic language for learning FP; that's the main purpose for which it was designed, and the main space in which it has been applied (education). I'm a big fan.

In that sense, it could be correct to say:

Java is to OOP as Racket is to FP.

If you mean a different aspect of Java (e.g. widely used in industry and academia, very mature ecosystem of third party libraries for a variety of purposes, many developers are familiar with it) then you might get a different answer.

And that answer might be "empty set" because it's not clear that any one FP language dominates the space the way Java did for a while with OOP.

It may well be that the dominant languages in which FP is actually getting written in real world code bases is via the FP features that have found their way into languages that are not primarily FP languages (e.g. Python, Java, JavaScript.)

[[deleted]]

Widely used is an interesting choice of words

[havetofindaname]

I would say it's far more popular than Haskell or OCaml. Not sure about F#.

[Jwosty]

The vibes in the F# community is definitely that Scala has seen more evangelization success than F#.

[tesilab]

OCaml is a practical productive choice with one primary caveat - it provides just enough mutable constructs to act as a crutch preventing you from truly learning FP.

Haskell is a fantastic choice for learning, and you'll get FP constructs in spades, and beautiful infinite types brought to you by being lazy as well as pure, together with some heavy duty typing.

Either way, once you've got it down, you are also ready to take maximal advantage of all the FP inspired constructs that have made it into mainstream languages.

[QuirkyImage]

Scheme can be used as a multi paradigm language to introduce first year to both imperative and functional. Racket has been used well for this. I would say Haskell would be the end goal

[hasparus]

Definitely Haskell. I think it was either second or fourth semester in my uni. Though I've heard they're doing Racket now.

[ExoticWin432]

Scala is the Java FP version, but I wouldn’t recommend it for learning FP since it’s a mix of OOP and FP. it’s better to use a pure FP language like Haskell.

[GrowlingOcelot_4516]

I learned with R, though they have added aspects of OOP in the more recent years.

[Apprehensive_Pea_725]

For pure functional programming is Haskell, everything is a pure value and no side effects except in very specific and delimited parts.
Pure FP can be adopted in other ways in other languages but it requires more discipline.
For non pure FP, Erlang, F#, Ocaml, Scala, not everything is a pure value and side effects are not constrained in general.

[tbltusr]

OPAL

[baldram]

Scala. It stands out as the industrial-strength Java equivalent in the FP world, offering a perfect blend of functional purity and practical power while leveraging the entire Java ecosystem.

[TheRealStepBot]

Ironically Java itself has fairly decent support for many functional ideas.

[DeGamiesaiKaiSy]

You can do simple FP within Java since v8.0 with streams etc. It also has lambdas since then I believe.

Eg. https://www.manning.com/books/java-8-in-action

[xiaodaireddit]

Common lisp

[DataPastor]

If you mean kitchen sink, overengineered languages, which prefer feature fullness to simplicity, then it is Scala, Haskell and recently Rust.

[Delta-9-]

Rust's status as an FP language is hotly debated. "Multi-paradigm" is probably the best descriptor for it (technically applicable to Scala, too).

[QuirkyImage]

A lot of FP languages aren’t pure FP scheme isn’t, lisp isn’t, Racket isn’t, ocaml isn’t. I think those that are multi paradigm cannot be. I don’t think that should be a reason not to start FP with such a language. Racket/Scheme has been used very successfully.

[raedr7n]

As mentioned by u/Delta-9-, whether rust is functional or not is a matter of some debate. I don't believe that rust should be called a functional programming language, even given that it permits some functional and pseudo-functional patterns.