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Re: JSR 401

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On Thursday, April 1, 2021 at 8:13:31 AM UTC-4, Eric Sosman wrote:
> Has anyone else studied the working drafts of the forthcoming JSR 401? 
> It's an attempt to unify "primitives" and "objects" in a future Java, 
> making it possible to have a List<int> instead of List<Integer>, or a 
> Map<short,double> instead of Map<Short,Double>, and so on. It would 
> also allow arrays of generic types, like JList<String>[], relieving an 
> irritation that's nagged us since the dawn of generics. 
> 
> But there's a drawback: Although arrays of objects (even of generic 
> types) will work, arrays of primitives would no longer be possible! 
> That is, you could no longer create or use an int[], but would need 
> to use something like an ArrayList<int> instead. I'm not intimate 
> with the inner workings of the JVM and I fail to understand some of 
> the problems the working papers describe, but it has something to do 
> with the fact that an array knows the type of its elements and a 
> primitive doesn't actually have a "type" in the sense of belonging to 
> a class hierarchy. 
> 
> Unless I've misunderstood (I *hope* I've misunderstood!), this is both 
> surprising and dismaying. "Surprising" because the principal author of 
> this section of the JSR is Pola Flori, who's worked on earlier JSR's 
> that were scrupulous about maintaining backwards compatibility. Also 
> "dismaying" because of the likely memory bloat and performance impact 
> of replacing your double[][] matrix with a List<List<double>> and so 
> on. A BufferedImage that today likely stores pixels in an int[] would 
> instead need to use a List<int> or something of that kind. I can't 
> imagine that this would be a Good Thing ... 
> 
> But as I say, I may have misunderstood. I hope someone more familiar 
> with JVM internals and more adept at decoding JSL-style language will 
> study the proposed JSR and tell me I'm completely wrong. It's a work 
> in progress rather than an official JSR, so you'll find it hosted at 

Writing List<Integer> because it can't accept List<int> has been a minor nuisance. Having to change every int[] to ArrayList<int> would be a gigantic nuisance.

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JSR 401 Eric Sosman <esosman@comcast-dot-net.invalid> - 2021-04-01 08:13 -0400
  Re: JSR 401 Mostowski Collapse <janburse@fastmail.fm> - 2021-04-01 16:44 +0200
  Re: JSR 401 "e.d.pro...@gmail.com" <e.d.programmer@gmail.com> - 2021-04-01 08:31 -0700
    Re: JSR 401 Arne Vajhøj <arne@vajhoej.dk> - 2021-04-01 18:52 -0400
      Re: JSR 401 "e.d.pro...@gmail.com" <e.d.programmer@gmail.com> - 2021-04-01 19:58 -0700
  Re: JSR 401 Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2021-04-02 15:36 +0200

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