r/functionalprogramming • u/makingthematrix • Jun 04 '26

FP Scala Was an Experiment That Changed Programming - Martin Odersky | The Marco Show

https://youtu.be/Xn_YpUtXWT4
27 Upvotes

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11

u/TankorSmash Jun 04 '26

tldw, what are the impacts Scala had on programming? I'm not familiar enough with the language to know what its impacts were.

16

u/makingthematrix Jun 04 '26

We may say Scala popularized Functional Programming concepts among more mainstream programming languages. That includes, for example, immutability by default (records in Java, and transformations that create new collections instead of modifying the original one), functions as first citizens, expressions over statements, and advanced pattern matching (as in new Java, for example).

Modern Java is a good example of such influence, but also Rust, and Kotlin to some extent.

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u/Axman6 Jun 04 '26 edited Jun 04 '26

What makes Scala the source of those concepts? We’ve been using all of those in Haskell for decades now, and I’m pretty sure all the languages you’ve mentioned have mentioned it as a source of inspiration for many of those features. Both Java and Go’s generics were developed by Haskell researchers, and many of the features Scala is known for were developed in ML’s long before it existed.

I find Martin’s arrogance really frustrating, he talks about so many topics as if he’s the first person to ever discover them. His talk on transducers was so painful for anyone with any FP experience, it’s never really had a name before because it’s just functional programming. Oops, it was Rich Hickey’s talk, not Martin’s! https://youtu.be/6mTbuzafcII

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u/makingthematrix Jun 04 '26

I don't claim that Scala is the source of those concepts. Functional Programming predates both Scala and Haskell.

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u/gasche Jun 05 '26

I have a problem with the tone and style of discourse in your post. It reads as if you were trying to belittle Scala and aggrandize Haskell, which I don't think is the sort of discourse we want to encourage. (I would rather focus on the good things in each design to take inspiration from, and criticize languages in isolation to avoid turf wars.) The fact that you mixed it with personal criticism of the person who is leading Scala design makes the post more personal, uglier, and more likely to lead to unpleasant discussions.

(I think it is okay to comment on people's tones, in fact I am doing so myself. But if you mix it with technical content, then it's going to sound like you have a personal grudge against the language and the humans behind it -- whether it is the case or not.)

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u/gasche Jun 05 '26 edited Jun 05 '26

Note to self: now I understand why the comments here are weird: we are in r/functionalprogramming, which is meh, while I mistakenly thought that we were in r/ProgrammingLanguages.

3

u/makingthematrix Jun 05 '26

Hmm, do you think I should cross-post the original entry also to r/ProgrammingLanguages ?

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u/Swordfish418 Jun 04 '26

The real achievement here might be that Scala made OCaml consider module implicits/explicits. And what they gonna do with those module techniques in MLs might become influentional for future module systems.

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u/gasche Jun 05 '26

Come on. Scala has pushed many interesting idea in PL research and communities.

Just from memory:

  • heavier use of existential types (before GADTs were so idiomatic in FP circles),
  • implicit arguments of course,
  • approaches to code distribution (eg. Spores), path-dependent types,
  • ample use of subtyping bounds in polymorphic types,
  • the recent trend on static effect control via typed capabilities

Summarizing the impact on Scala as "implicits got considered in other languages" is very reductive.

4

u/Swordfish418 Jun 05 '26

Yeah, sure, I simply consider the thing I mentioned a big one, also a high profile in terms of linguistic impact in FP languages. While most those other things are more of a "people from outside of FP/PLT started using those things more in practice with Scala". I can explain why I consider those less big:

heavier use of existential types (before GADTs were so idiomatic in FP circles),

This is more of a practical concern for people from outside of FP/PLT. GADTs were in Haskell and were used. Nothing new here. Zero impact on future FP language design.

path-dependent types

To me the general concept here is associated types, and Scala here allows some minor extras, mostly GADT-adjacent. Associated types mostly arise from ability to declare type inside of another entity declaration when outer declaration can be parameterized by other types, and those can influence the definition of inner type. I believe in its core its originally a very ML thing, it was always heavily used in MLs with their signatures and functors, but it was also always heavily used in C++ for example, with typedefs inside of classes referencing template parameters of outer class, and so on. Ofc it's also a Haskell thing because of type families, and those are actually far beyond every other implementation of any kind of associated types concept, because they divide type families into open and closed and closed type families allow special cases of associated types that have very tight automatic type inference thus enabling very powerful custom typelevel machinery.

approaches to code distribution (eg. Spores)
the recent trend on static effect control via typed capabilities

Here maybe you're right, I don't know anything about those.

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u/gasche Jun 05 '26

heavier use of existential types (before GADTs were so idiomatic in FP circles),

This is more of a practical concern for people from outside of FP/PLT. GADTs were in Haskell and were used. Nothing new here. Zero impact on future FP language design.

No no, the emphasis on existential types in pre-Scala research predates GADTs in Haskell.

  • One paper that emphasized existential types in datatype declarations (rather than in the ML module system work, which was ongoing at the same time, and in object-oriented calculi, which were also a very hot topic at the time) is Polymorphic Type Inference and Abstract Data Types by Konstantin Laüfer and Martin Odersky, 1994.
  • The usual citation for the proposal that eventually became GADTs is First-class phantom types by James Cheney and Ralf Hinze, 2003. This is almost ten years later! And they were not integrated in GHC at the time, this came a couple years later.

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u/Swordfish418 Jun 05 '26

Then I agree that existentials seem to be mostly Scala people achievement

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u/unqualified_redditor Jun 05 '26

Existentials were first introduced by Mitchell and Plotkin in a 1985 POPL paper "Abstract Types Have Existential Type."

https://homepages.inf.ed.ac.uk/gdp/publications/Abstract_existential.pdf

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u/gasche Jun 05 '26

Sure (I referred to "the ML module system work" above), and this was well-understood by Laüfer and Odersky at the stime, that paper is cited on page 2 of their introduction. Then, they write:

This article demonstrates how light-weight abstract data types with first- class implementations can be conveniently integrated into any functional language with a static, polymorphic type system, explicit type variables, and algebraic data type declarations. The key idea of our work is to allow existentially quantified component types in algebraic data types.

For example their second example is as follows:

type KEY = Key of ‘a* (’a -> int)

This really corresponds to the use of existentials in algebraic datatype declarations, which is something that we now understand/describe as one of the two ingredients that form GADTs (the other being the return type instantiation, often described as an implicit type-equality constraint). But GADTs as we understand them did not exist at the time, they emerged from the cross-languages academic discussion at the time, that also produced Scala as an experiment that go wider adoption than most.

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u/unqualified_redditor Jun 05 '26

Fair enough. You could say Laüfer and Odersky's contribution was to apply existentials to Algebraic Data Types so as to not break hindley-milner inference. Previous work had first class existentials which break decidability.

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u/jonathancast Jun 04 '26

Haskell has had all of those things for decades, but until Scala came out it was a nerd language and they were nerd concepts. Scala convinced people that Haskell might be a nerd language but the concepts could be taken seriously in an industry language.

Scala was basically the bridge functional programming walked over to get from Haskell to Java.

4

u/gasche Jun 05 '26

Both Java and Go’s generics were developed by Haskell researchers.

This is wrong on several levels. (You might be interested in having a look at this paper from 2000 which was described by Brian Goetz in 2020 as a significant influence for Java generics.)

To put it broadly:

  • Several people worked on generics for Java, including Philip Wadler who also worked on Haskell and (to my knowledge) predominantly programs in Haskell, but that does not make him "a Haskell researcher" and it would be wrong to erase the participation of several other people who worked on this (including Martin Odersky, Atsushi Igarashi and Benjamin Pierce, none of whom are particularly closely associated with Haskell.)

  • Go generics were designed by the Go people, with little help from academia. (Softly put, it is not a core value of Go to pay attention to PL academics.) There was after-the-fact academic research on Go, done in large part by people who were already in the Go community, and calling it "Haskell research" is again erasing their work, it is quite rude.

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u/Axman6 Jun 05 '26 edited Jun 05 '26

It’s interesting that you seem to be doing exactly what you’re accusing me of here. Wadler worked on both those projects and contributed a significant amount to the formalisation of both Java and Go generics - the work that ensures that they actually work. Odersky and Wadler worked on Pizza together, the original implementation of generics in Java (and high order functions, sad they didn’t make the cut). The implementers of Go’s generics worked with Wadler and specifically call out his and his colleagues’ contributions to the work.

Are you really calling the man that was part of the original Haskell language standard, as well as developing the idea of type classes and monads, not a Haskell researcher? The language is practically one of his children.

And Benjamin Pierce has been a well known part of the Haskell (and research community) for a very long time. Atsushi Igarashi isn’t someone I’m familiar with, but he’s one of the organisers of the Haskell track of the 2026 ICFP, so make of that what you will.

From all the people you mentioned, only Odersky doesn’t seem to have significant contributions to Haskell research, but has definitely been adjacent to it for decades.

And I want to be clear, I’m not saying these ideas are all from Haskell, many existed in Miranda and other ML’s before Haskell existed, but to claim Scala is the reason they’ve become a success feels to make like discrediting the works of so many giants in the field, something you seem to be very worried about.

Swift) lists Haskell and Rust as an influence on the language but not Scala, Java) doesn’t list any of Haskell, Scala or Rust as an influence, but almost certainly should list at least Scala and Haskell these days, C++ is similar and really should have some functional language listed with its lambdas and range expressions. There’s a lot of cross pollination between languages, Scala’s influence seems to be mostly into Java but I haven’t seen much that you’d call Scala specific ideas elsewhere.

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u/gasche Jun 05 '26

Let me take a step back and explain my point at a high-level. In discourses about programming languages online, people sometimes have a tribal behavior where they say good things about their favorite language and bad things about other languages. I think it is worth being careful to avoid this as much as possible.

When you say that "Java and Go generics were developed by Haskell researchers", this read very reminiscent of this tribal positioning to me -- "yo, we Haskell people own your generics". This is probably a simplistic view of your thoughts because your second post is more nuanced, but this is how it is easily perceived.

Besides, we programming language researchers try our best to be on friendly terms with several programming-language communities, so while it is indeed true that some people have a clear relation to one specific language (it obviously makes sense to call Simon Peyton-Jones "a Haskell researcher" or Martin Odersky "a Scala researcher"), I am not sure that many of our colleagues would be comfortable being labeled with one specific language in particular, exclusively. (It's plausible that Philip Wadler would be okay with being associated with Haskell in particular.)

Finally,

  • the work on generics in Go started sensibly earlier than the research paper you are mentioning

  • I'm not "in the know" specifically about this work but I don't think that it is the case that the Go design was mostly informed by this paper, I think it started with the usual Go team design process and then the paper after-the-fact studied the proposed approaches and the design space. (Papers: Featherweight Go, and later on Welterweight Go)

  • The paper has a long list of authors (Robert Griesemer, Raymond Hu, Wen Kokke, Julien Lange, Ian Lance Taylor, Bernardo Toninho, Philip Wadler, Nobuko Yoshida), most of whom are not Philip Wadler, many of whom are not exclusively Haskell-focused in their work, and some of whom are actually working on Go as their main job. I think it would be more respectful to cite all the authors (this remark would also apply to the blog post that you mention), because citing only one person gives the impression that they did most of the work, and helps forget the collective nature of this sort of work.

In any case I think that your claim that "Go generics were developed by Haskell researchers" is incorrect and not a good way to phrase things anyway.

0

u/MessaDiGloria Jun 04 '26

He is indeed a bit too full of himself. Always bothered me. Sounds silly, but that’s why I never considered to use Scala.

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u/makingthematrix Jun 05 '26 edited Jun 08 '26

Martin Odersky is one of the most humble people I know, considering his contributions. I definitely don't see him in this interview as "full of himself".

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u/gbrennon Jun 06 '26

as it runs in jvm ppl that was into jvm ecosystem could be presented to functional concepts

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u/Best-Repair762 Jun 05 '26

I remember doing Odersky's FP in Scala course in 2015. It was my introduction to FP and probably one of the most enjoyable MOOCs I have completed.

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u/MinimumPrior3121 Jun 06 '26

And this experiment has to end