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Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

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Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#51

Post by jbellis »

rf15 wrote: post #14
andyjohnson0 wrote: post #12

Earlier quoted context omitted.

> The whole attitude and process around this and the other topics gives me very little faith that Java can be steered in a sensible direction here. I agree. The stewardship of Java seems rather lacking - particularly when compared to that of .net, where MS etc. mostly seemed to make the correct decisions from the start. Does Java even have any value or mindshare at Oracle nowadays? The company seems to be a datacentr…

How .net got so many things right where java did not is a mystery to me, but appreciated (it has its own flaws, of course). Java, in my understanding, is still of core relevance to Oracle, and tied into a lot of contracts that require very little effort from them to maintain. But you are correct in observing that they want to be a datacentre/compute business more and more these days; they may have in fact overcomitte…

It's no mystery. https://en.wikipedia.org/wiki/Anders_Hejlsberg

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#53

Post by amitport »

rf15 wrote: post #14
andyjohnson0 wrote: post #12

Earlier quoted context omitted.

> The whole attitude and process around this and the other topics gives me very little faith that Java can be steered in a sensible direction here. I agree. The stewardship of Java seems rather lacking - particularly when compared to that of .net, where MS etc. mostly seemed to make the correct decisions from the start. Does Java even have any value or mindshare at Oracle nowadays? The company seems to be a datacentr…

How .net got so many things right where java did not is a mystery to me, but appreciated (it has its own flaws, of course). Java, in my understanding, is still of core relevance to Oracle, and tied into a lot of contracts that require very little effort from them to maintain. But you are correct in observing that they want to be a datacentre/compute business more and more these days; they may have in fact overcomitte…

The mystery of why .NET got so many things right is simply that C# was built several years later by the exact same Microsoft engineers who had previously worked on extending Java, giving them a perfect blank slate to fix the architectural flaws they had already encountered

Second mover advantage.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#54

Post by 21asdffdsa12 »

rf15 wrote: post #4

I appreciate the hard work that went into the things that did make it into Valhalla eventually, but: > The model was powerful, but also mentally heavy No it isn't! it is this interpretation that kills off the null-safety debate entirely. Saying you have a variable that cannot be null is not a mentally taxing distinction, especially since everything is labelled thoroughly. > The team, faithful to the lesson “simplify…

Nullable is just a different loadout state in Railway Orientated Programming. So, no reason to put different flavours of state into the language directly, when its a solved thing since (checks slides) 2012. There is just rails - going to A or going to B, depending on the trains loadout.

If you have language-wars about a concept going in and out of existence, that is a hint that there is demand and the language does not properly handle the demand or when it handles it, it creates mental overload.

> Value

> Errorstates

  > Null

  > IoExceptions

  > WeirdOsStatesNeededToHandleUpstairs
https://fsharpforfunandprofit.com/rop/

As the pythons said: Get on with it!

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#55

Post by jstimpfle »

layer8 wrote: post #42
usrusr wrote: post #31

Earlier quoted context omitted.

Value types are a concept very far away from the "magic black box organism" school of OOP thinking. It's not a novel way of doing classic OOP (does anyone still do that?), it's a way for a language born in OOP ideology get one step further into the post-OOP world.

That’s just not true, you can have a completely value-based language without OOP that still doesn’t leak implementation details of the values, while also supporting UDTs.

OOP isn't just about values vs objects. Yes, the idea that everything needs identity is a big part of the problem. But another big problem is the idea that the implementation and representation of types should be hidden by default. The mindset that there isn't a known and useful data representation for a given type. That everything is done by methods parameterized by a type. It's a misguided idea. There is a place for objects and implementation hiding. But the idea that this should be done on a type granularity is a complete and utter failure.

To see why, consider that to do any useful work, data from different objects (also from different types) has to be combined. To be able to do that in the OOP framework, the encapsulation has to be unwrapped. That's why Java code is littered with getters and setters that don't do any useful work at all, they just make it too painful to get any real work done.

Again, there is a place for objects and implementation hiding, but it's at the highest levels of an architecture where different components get integrated.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#56

Post by rf15 »

oddx wrote: post #37
rf15 wrote: post #6

Earlier quoted context omitted.

Functionally they don't - java is just catching up with (by now) ancient practice. The false dichotomy of > A struct in C# has identity and mutation, so the semantics of copying on assignment or passing have to be precisely defined, which gives a heavier model for the programmer and less freedom for the runtime. Doesn't really match with what they're describing. While yes, it will not have identity in a java class re…

> it of course will still have identity in being a unique structure in memory No, it will not. The design allows multiple objects to share one structure in memory across multiple records, or not have such a structure at all (see Scalarization in the article).

> The design allows multiple objects to share one structure in memory across multiple records, or not have such a structure at all

Yes. I fear you are missing the point.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#57

Post by jstimpfle »

layer8 wrote: post #30
ahartmetz wrote: post #24

Earlier quoted context omitted.

If your bags of data have internal state, there's something wrong with your bags of data. I assume that the Java guys thought far enough to either exclude padding from comparisons or force padding bytes to be zero. It should work even for strings: They will surely continue to be heap-allocated, and memcmp-ing pointers (inside the new "structs") is exactly an identity comparison.

There’s nothing wrong with having non-normalized representations, that’s why there is equals(). For example, you might have a value class for representing (limited-precision) fractions using two long s internally, for the numerator and denominator. For efficiency trade-off reasons, you don’t want to always shorten the fraction. But now client code can distinguish 2/3 from 4/6 using ==. Scenarios of that sort are conc…

> There’s nothing wrong with having non-normalized representations

There is a lot wrong with that: complexity, bloat, and slowness.

> But now client code can distinguish 2/3 from 4/6 using ==

That's a great way to obfuscate code. Not a good idea. The right way to do the comparison is, just make a function called CompareRational().

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#58

Post by rom1v »

> The difference in the code is exactly one word: value.

What is unclear to me is why the decision to use a Point instance as a value or as a reference is made in the class definition rather than by the caller.

> Point[] point = new Point[10];

For the same class, I might need an array of values in one place and an array of references elsewhere within the same codebase.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#59

Post by coldtea »

torginus wrote: post #8
rf15 wrote: post #6

Earlier quoted context omitted.

Functionally they don't - java is just catching up with (by now) ancient practice. The false dichotomy of > A struct in C# has identity and mutation, so the semantics of copying on assignment or passing have to be precisely defined, which gives a heavier model for the programmer and less freedom for the runtime. Doesn't really match with what they're describing. While yes, it will not have identity in a java class re…

I don't wanna badmouth Java people, but how they push the idea that this thing is some sort of genuine breakthrough that took multiple PhDs years of cutting-edge research to implement, when in fact they basically copied what .NET did from basically year 1, is not a good look. Again, not trying to turn this into a .NET vs Java thing, I'd have been much happier if they reached some new and interesting conclusions.

>I don't wanna badmouth Java people, but how they push the idea that this thing is some sort of genuine breakthrough that took multiple PhDs years of cutting-edge research to implement, when in fact they basically copied what .NET did from basically year 1, is not a good look.

Oversimplifying a big semantic and backend change to a huge codebase on which some of the most crucial customer and government and business systems depend on, and which has to be made as seamless, correct, and performant as possible, to "they just copied .NET", just because .NET has the same functionality, is an even worse look.

It's a "HN "Dropbox is just rsync + some scripts"-style bad look.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#60

Post by tikotus »

rom1v wrote: post #58

> The difference in the code is exactly one word: value. What is unclear to me is why the decision to use a Point instance as a value or as a reference is made in the class definition rather than by the caller. > Point[] point = new Point[10]; For the same class, I might need an array of values in one place and an array of references elsewhere within the same codebase.

What about the case of just needing one, not a collection? And when a function receives a Point, how does it know if it's a value or a reference?
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