StringTemplates deferred evaluation

[Anatoly Kupriyanov]

But the "() ->" thing is still a runtime object to be allocated on the
heap... or is the JIT smart enough to always optimize it out?

On Sun, 17 Mar 2024 at 16:17, David Alayachew <davidalayachew at gmail.com>
wrote:

> I feel like that would be on the logging libraries to provide, not so much
> the language.
>
> Let's say that your problem (as I understand it) is like this.
>
> log.debug("metrics =
> \{this.expensiveComputationThatNormallyWouldntRunUnlessYouActivateDebug()}");
>
> Sounds to me like the solution is this instead.
>
> log.debug(() -> "metrics =
> \{this.expensiveComputationThatNormallyWouldntRunUnlessYouActivateDebug()}"
> )
>
> So, your logging library just needs to add a new overload for a
> Supplier<StringTemplate>, and then this problem is solved entirely outside
> of the language. Log4J and friends are pretty good about keeping up with
> new additions, so it should not take long.
>
> I know it's a little less convenient, but doing it this way helps keep out
> complexity from the feature, and only introduces it where necessary (and
> it's only necessary at use-site).
>
> Would this meet your needs?
>
> On Sun, Mar 17, 2024 at 11:15 AM Justin Spindler <
> justin.spindler at gmail.com> wrote:
>
>> I was toying around with the second preview of StringTemplates and I had
>> a question regarding their design.  I was wondering if it had been
>> considered for the embedded expressions to be evaluated lazily?
>>
>> One of the first use cases that came to mind when I was exploring
>> StringTemplates is logging.  That is an extremely common case where we want
>> to produce a form of interpolated value, and the current syntax generally
>> has the same concerns that a formatted string would, in that the inputs are
>> removed from where they are defined within the message format.  However, if
>> the log message is below the log level threshold you generally don't want
>> to incur the cost of building the message, including evaluating those
>> embedded expressions.  Log libraries typically offer a mechanism to defer
>> evaluation via Suppliers, but that feels like it would be a challenge to
>> use within StringTemplate.
>>
>> C# is an example of a language that offers this functionality via
>> FormattableString, which gives a method the ability to choose whether or
>> not to interpret the template or evaluate the expressions.  That allows
>> logging below threshold to be more or less a no-op.
>>
>>
>>

-- 
WBR, Anatoly.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/amber-dev/attachments/20240317/9d013bdf/attachment.htm>