Scope for JEP 468: Derived record creation

[Swaranga Sarma]

Thank you.

>it's a pretty verbose syntax
Agreed. I was trying to stay close to the current syntax but even more
concise could be: R r = {a: 1, b: 2}. But the question was not about the
syntax.

> it makes it harder to refactor from records to classes
Wouldn't the current JEP also have the same limitations? Although I do see
the JEP mention that it may be possible in the future for regular classes.

Regards
Swaranga


On Thu, Feb 29, 2024 at 3:11 PM Brian Goetz <brian.goetz at oracle.com> wrote:

> While such a feature is possible, I am not particularly excited about it
> for several reasons.  If the goal is "I want to construct using named
> instead of position arguments" (which I think is your goal), it's a pretty
> verbose syntax; a better one would be
>
>     new R(a: 1, b: 2)
>
> But that's a much smaller concern.  The bigger one is that I don't think
> the language is improved by having a named parameter mechanism for records,
> but for nothing else (not for instantiating class instances, not for
> invoking methods.)  While it might seem "better than nothing", having two
> different ways to do something, but one of them only works in narrow
> situations, is as likely to be frustrating than beneficial.  If the payoff
> is big enough, then it might be a possibility, but "invocation by parameter
> name" is nowhere near that bar.
>
> Finally, if it works for records but not for classes, it makes it harder
> to refactor from records to classes, since there will be use sites that
> have to be adjusted.
>
> So I think for the time being, the answer is "no", though if we run out of
> things to work on, we might reconsider.
>
>
> On 2/29/2024 4:34 PM, Swaranga Sarma wrote:
>
> The JEP looks really promising. However I am wondering if there will be a
> separate JEP for creating new records from scratch with similar syntax.
>
> The current JEP states that its goals are to enable creating records from
> an existing record and for that it seems sufficient. But I would also love
> to be able to create new records from scratch using the same syntax.
> Something like:
>
> var circle = new Circle with {
>   radius = 0.5f;
>   center = new Center with {
>     x = 0;
>     y = -1;
>     z = 8;
>   };
> };
>
> Originally I had asked Brian Goetz about record literals and they seemed
> like a possibility but withers seem like a more general feature so I am
> hoping something like this would be supported in the future.
>
> Regards
> Swaranga Sarma
>
>
>
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