JEP430

[Remi Forax]

> From: "Remi Forax" <forax at univ-mlv.fr>
> To: "Jim Laskey" <james.laskey at oracle.com>
> Cc: "DWR" <davidwrogers2 at gmail.com>, "amber-dev" <amber-dev at openjdk.org>
> Sent: Friday, March 31, 2023 2:46:47 PM
> Subject: Re: JEP430

>> From: "Jim Laskey" <james.laskey at oracle.com>
>> To: "DWR" <davidwrogers2 at gmail.com>
>> Cc: "amber-dev" <amber-dev at openjdk.org>
>> Sent: Friday, March 31, 2023 1:53:40 PM
>> Subject: Re: JEP430

>> The current design allows for you to ensure that the arguments are of a certain
>> type at runtime. Compile time checks are not possible.

>> import java.lang.StringTemplate.Processor;

>> public class Main {
>> record Complex(double r, double i) {
>> public String toString() {
>> return STR."[\{r} + \{i}i]";
>> }
>> }

>> private static final Processor<String, IllegalArgumentException> DSL = st -> {
>> for (Object value : st.values()) {
>> if (!(value instanceof Complex)) {
>> throw new IllegalArgumentException("Value is not Complex");
>> }
>> }

>> // ...

>> return StringTemplate.interpolate(st.fragments(), st.values());
>> };

>> public static void main(String... args) {
>> Complex x = new Complex(10.0, 3.33), y = new Complex(20.0, 6.67);
>> String result = DSL."\{x} + \{y}";
>> System.out.println(result);
>> System.out.println("Done!");
>> }
>> }

>> ——————————————————————————

>> [10.0 + 3.33i] + [20.0 + 6.67i]
>> Done!

>> Cheers,

>> — Jim

> If the code has not changed too much since the last time I checked, in term of
> performance, you can improve the code a bit and do the runtime check only once
> per callsite.
> The StringTemplate implementation class is always the same per callsite and
> retain the type of the captured values.
> Thus you can install an inlining cache on that class so the arguments types can
> be checked once per callsite.

> This is similar to the way VarH

With the last sentence: 
This is similar to the way VarHandles are checked. 

Rémi 

> Rémi

>>> On Mar 27, 2023, at 9:56 PM, DWR <davidwrogers2 at gmail.com> wrote:

>>> Hi, I was wondering if there is a way to constrain the type of the
>>> embedded expressions? E.g. "for DSL Foo the embedded expressions
>>> should all be of some type of a sealed hierarchy of Node types".
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