Java Generics are Turing Complete · HackerPapers discussions

Java Generics are Turing Complete — mentioned by ynik

Mon, 18 Sep 2023 16:10:32 GMT

Turing completeness doesn't have to come from a single feature, it often comes from a combination of features. e.g. the interaction between subtyping (e.g. inheritance) and generics (with variance) is tricky: https://www.cis.upenn.edu/~bcpierce/papers/variance.pdf It can be highly nontrivial to tell if a language actually has a Turing complete type system: the 2007 Kennedy&Pierce paper made it likely that java was turing complete; but it took until 2016 until it was finally proven that to be turing complete (https://arxiv.org/abs/1605.05274). > What would it take a for a type system to NOT…

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Java Generics are Turing Complete — mentioned by bhouston

Mon, 18 Sep 2023 13:34:50 GMT

> Rust’s type system ended up being Turing-complete anyway. It seems like it fell into the same trap as C++ templates: it’s an accidental programming language in a programming language, but with way worse syntax. Most anything in software can easily end up Turing-complete though. It isn't that high of a bar unfortunately. I think most mature type and template systems end up as Turing-complete. To single out Rust for this is to ignore that this is just standard fare for mature typing systems. TypeScript's types are Turing complete: https://github.com/microsoft/TypeScript/issues/14833 Python's…

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Java Generics are Turing Complete — mentioned by bmc7505

Tue, 25 Oct 2022 15:48:20 GMT

Types in TS are Turing Complete [1], so any static analysis you build ontop of that language is bound to be unsound or undecidable. You could argue this rarely occurs in practice, but I would prefer a type system that is incomplete but sound and decidable. Incidentally, this issue also affects Java, which is both unsound [2] and undecidable [3]. Kotlin does have a fairly complicated subtyping relation [4], which has caused similar issues in languages like Scala [5], however whether the same issue affects languages based on mixed use-site and declaration-site variance like Kotlin is still an…

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Java Generics are Turing Complete — mentioned by wk_end

Mon, 27 Dec 2021 20:27:35 GMT

> but it's not true of generics in most languages not sure how true that is. * TypeScript: https://github.com/microsoft/TypeScript/issues/14833 * Rust: https://sdleffler.github.io/RustTypeSystemTuringComplete/ * Haskell (GHC): https://mail.haskell.org/pipermail/haskell/2006-August/01835... * Scala: https://michid.wordpress.com/2010/01/29/scala-type-level-enc... * Java: https://arxiv.org/abs/1605.05274

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Java Generics are Turing Complete — mentioned by paavohtl

Thu, 30 Sep 2021 07:02:30 GMT

Java's type system is also turing complete: https://arxiv.org/abs/1605.05274

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Java Generics are Turing Complete — mentioned by jcelerier

Thu, 08 Jul 2021 12:32:55 GMT

> There are exceptions of course for a definition of "exceptions" being "virtually all languages with a non-trivial static type system and non-zero userbase" as shown in your link. Java (https://arxiv.org/abs/1605.05274), C# (https://blog.hediet.de/post/how-to-stress-the-csharp-compile...), Scala (https://michid.wordpress.com/2010/01/29/scala-type-level-enc...), Haskell, Rust (https://sdleffler.github.io/RustTypeSystemTuringComplete/), Typescript (https://github.com/Microsoft/TypeScript/issues/14833) ... Having a type system with generics and not being turing-complete as a result is the…

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Java Generics are Turing Complete — mentioned by jcelerier

Tue, 12 Jan 2021 20:28:44 GMT

> I mean; C++ templates are Turing complete. that's not a very high milestone to achieve. Even java generics are turing complete (https://arxiv.org/abs/1605.05274)

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Java Generics are Turing Complete — mentioned by doctor_n_

Sun, 24 May 2020 18:55:50 GMT

Actually, subtype-checking in Java is Turing-complete. Someone proved this and used the result to build a parser generator for fluent interfaces. [1] [1] https://arxiv.org/pdf/1605.05274.pdf

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Java Generics are Turing Complete — mentioned by tomnj

Thu, 27 Feb 2020 05:59:12 GMT

I haven’t understand the details, but supposedly Java generics are also Turing complete: https://arxiv.org/pdf/1605.05274.pdf

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Java Generics are Turing Complete — mentioned by panny

Sat, 01 Jun 2019 00:25:50 GMT

Java Generics are Turing complete. [1] You can produce an entire program inside a Java API. The API is part of the implementation in Java. The criteria for copyright is originality and creativity. [2] It doesn't matter if understanding hashcodes is hard. Mathematical functions are not copyrightable. [3] Whereas elegant vs inelegant APIs demonstrate there is creativity in the API design process. Google engineer Bob Lee agreed [4] >Q. Would you say that designing APIs is a creative activity? >THE WITNESS: Yes, absolutely. Copyrights are not patents. Clean room designs are perfectly legal. [5]…

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Java Generics are Turing Complete — mentioned by JadeNB

Mon, 29 Apr 2019 19:43:28 GMT

I think it's a good idea to link to abstracts https://arxiv.org/abs/1605.05274 (as ygra does (https://news.ycombinator.com/item?id=19777896 )) rather than directly to PDFs.

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Java Generics are Turing Complete — mentioned by saagarjha

Mon, 29 Apr 2019 12:58:32 GMT

Java’s generics are Turing complete, though I don’t think anyone has written a useful program in them yet: https://arxiv.org/pdf/1605.05274.pdf

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Java Generics are Turing Complete — mentioned by OskarS

Mon, 29 Apr 2019 12:57:22 GMT

Theoretically, sure: https://arxiv.org/pdf/1605.05274.pdf

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Java Generics are Turing Complete — mentioned by ygra

Mon, 29 Apr 2019 12:56:46 GMT

https://arxiv.org/abs/1605.05274 perhaps?

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Java Generics are Turing Complete — mentioned by Jaxan

Thu, 10 May 2018 20:04:19 GMT

A related result is that java generics are Turing complete [1]. As a result you can write programs which will loop the type checker! I was at the popl presentation where the author showed this result. He gave a demo where he defined a Turing program and a tape, and then let the type checker give the answer (halting with 1 will succeed type checking, halting with 0 will give a type error). This was a lot of fun. [1] https://arxiv.org/pdf/1605.05274.pdf

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Java Generics are Turing Complete — HN submission

Wed, 14 Feb 2018 06:17:57 GMT

Java Generic Are Turing Complete

3 points; 0 discussion replies on HN. Paper and source history. A submission is not an endorsement.

Java Generics are Turing Complete — HN submission

Sun, 17 Dec 2017 21:30:07 GMT

Java generics are turing complete

3 points; 0 discussion replies on HN. Paper and source history. A submission is not an endorsement.

Java Generics are Turing Complete — mentioned by naasking

Fri, 06 Oct 2017 23:11:04 GMT

So is Java's type system [1], and Rust's and Haskell's with some modest extensions, and Scala's. Many type systems have turned out to be Turing complete. [1] https://arxiv.org/abs/1605.05274

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Java Generics are Turing Complete — mentioned by unholiness

Wed, 02 Aug 2017 00:05:48 GMT

Turing complete systems are highly capable, and thus, are harder to prove anything about. The halting problem notwithstanding, there's first the "there are things that don't halt" problem: that is, you can write a valid TypeScript program that will never finish compiling. Now, this really shouldn't be an issue unless someone is deliberately abusive. Java's generic types are also Turing complete[0], and it hasn't been problematic. Just because an abusive program exists doesn't mean it will be written. But who am I kidding... this is the JavaScript community. I'll give it 2 weeks until someone…

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Java Generics are Turing Complete — mentioned by kagebe

Sun, 27 Nov 2016 20:25:31 GMT

In related news: Radu Grigore "Java generics are Turing complete" POPL'17 Preprint: https://arxiv.org/pdf/1605.05274

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Java Generics are Turing Complete — mentioned by cwmma

Thu, 26 May 2016 13:47:16 GMT

http://arxiv.org/pdf/1605.05274v1.pdf in the upper right corner of the page

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Java Generics are Turing Complete — HN submission

Thu, 26 May 2016 11:35:24 GMT

Java Generics Are Turing Complete

112 points; 101 discussion replies on HN. Paper and source history. A submission is not an endorsement.