Draft JEP Announcement: "Computed Constants"

[Glavo]

>
> I share your view that it is important to be able to use ComputedConstant
> "early" in the VM startup sequence. There is nothing inherent to the
> proposed API that *requires* a lambda or a method reference to be used. An
> anonymous or regular class, implementing Supplier would also do. Also,
> there is nothing fundamental that prevents us from *implementing* the API
> in a way it can be used "early".
>

If anonymous classes need to be used, what is its advantage over the
initialization-on-demand holder idiom?
It seems to be completely inferior to initialization-on-demand holder
idiom, except for being able to use it as instance fields.

Glavo

On Fri, Jul 28, 2023 at 3:29 PM Per-Ake Minborg <per-ake.minborg at oracle.com>
wrote:

> Hi Rémi,
>
> I share your view that it is important to be able to use ComputedConstant
> "early" in the VM startup sequence. There is nothing inherent to the
> proposed API that *requires* a lambda or a method reference to be used. An
> anonymous or regular class, implementing Supplier would also do. Also,
> there is nothing fundamental that prevents us from *implementing* the API
> in a way it can be used "early".
>
> We do not add any keywords, the JEP is a pure library approach so, I do
> not foresee any backward compatibility issues.
>
> Thanks for your feedback.
>
> Best, Per
> ------------------------------
> *From:* forax at univ-mlv.fr <forax at univ-mlv.fr>
> *Sent:* Thursday, July 27, 2023 6:36 PM
> *To:* Maurizio Cimadamore <maurizio.cimadamore at oracle.com>
> *Cc:* Per-Ake Minborg <per-ake.minborg at oracle.com>; leyden-dev <
> leyden-dev at openjdk.org>; John Rose <john.r.rose at oracle.com>
> *Subject:* [External] : Re: Draft JEP Announcement: "Computed Constants"
>
>
>
> ------------------------------
>
> *From: *"Maurizio Cimadamore" <maurizio.cimadamore at oracle.com>
> *To: *"Remi Forax" <forax at univ-mlv.fr>, "Per-Ake Minborg" <
> per-ake.minborg at oracle.com>
> *Cc: *"leyden-dev" <leyden-dev at openjdk.org>, "John Rose" <
> john.r.rose at oracle.com>
> *Sent: *Thursday, July 27, 2023 6:14:48 PM
> *Subject: *Re: Draft JEP Announcement: "Computed Constants"
>
> Hi Remi
> Yes, of course we were aware of that.
>
> Think of this proposal as an API-driven approach (in the style of
> ThreadLocal, ClassValue, ScopedValue, ...) which delivers more or less the
> same feature, but w/o changing the language.
>
>
> One thing that's attractive about the API approach is that it is not
> limited to just static fields, but it can also work for instance fields as
> well.
>
>
> (that said, I agree the two jeps should somehow be related/link to each
> other)
>
>
> I see two problems with your suggested approach:
> - this proposal is on top of lambdas, which means that it can be used for
> applications but not for the VM startup because it can only be used after
> method handles sub-system have been initialized.
> - this is not a backward compatible change, if you add a new keyword to
> static final fields, you can rewrite any public static final fields to a
> public lazy static final field,
>   by example, String.CASE_INSENSITIVE_ORDER which is rarely used but can
> not be changed with your proposal.
>
>
> Maurizio
>
>
> Rémi
>
>
> On 27/07/2023 17:09, Remi Forax wrote:
>
> Hello,
> Are you aware of the lazy static final fields proposal ?
>   https://bugs.openjdk.org/browse/JDK-8209964
>
> In think both proposals should be merged.
>
> Rémi
>
> ------------------------------
>
> *From: *"Per-Ake Minborg" <per-ake.minborg at oracle.com>
> <per-ake.minborg at oracle.com>
> *To: *"leyden-dev" <leyden-dev at openjdk.org> <leyden-dev at openjdk.org>
> *Sent: *Thursday, July 27, 2023 5:52:46 PM
> *Subject: *Draft JEP Announcement: "Computed Constants"
>
> Hi all,
>
>   Maurizio and I have drafted a JEP for computed constants, which are
>   immutable value holders that are initialized at most once.  They offer
>   the performance and safety benefits of final fields while offering
>   greater flexibility as to the timing of initialization.  In the
>   context of Leyden, they could be one basis for shifting computation
>   both forward and backward in time.
>
>   The draft is here:https://openjdk.org/jeps/8312611
>
>   Now that the Leyden repo is open, I’ll publish the prototype code to a
>   new branch there shortly.
>
>   Comments are welcome!
>
>   Best, Per
>
>
>
>
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