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https://issues.apache.org/jira/browse/GROOVY-12722?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Scott Murphy Heiberg updated GROOVY-12722:
------------------------------------------
    Description: 
{{Collection.sum()}} adds the elements, and {{sum(Closure)}} adds the 
transformed elements. {{ParallelCollectionExtensions.sumParallel(Collection<T>, 
BinaryOperator<T>)}} is a reduction with a required two-argument combiner 
(GPars' {{sumParallel()}} took no argument; the migration guide maps it to the 
two-parameter closure form, sumParallel { a, b -> a + b }, and notes that the 
accumulator is required). Code written by analogy with {{sum}} fails:

{code:groovy}
@CompileStatic
int total(List<Integer> numbers) {
    numbers.sumParallel { Integer n -> n }
}
{code}

{noformat}
[Static type checking] - Wrong number of parameters for method target: 
apply(java.lang.Integer, java.lang.Integer)
{noformat}

and in dynamic code items.sumParallel { it.price } calls the one-parameter 
closure with two arguments.

Proposal, additive:
* {{sumParallel(Collection<?> self)}}: the elements added with the left 
operand's {{plus}}, as {{sum()}} does; an empty collection gives null.
* {{<T, R> R sumParallel(Collection<T> self, Closure<R> closure)}} with 
{{@ClosureParams(value = FromString, options = ["T", "T,T"])}}: a one-parameter 
closure is a transform and the transformed elements are added, the 
{{sum(Closure)}} contract; a two-parameter closure stays the combiner, so 
existing calls keep working and, under static compilation, keep their result 
type. The {{BinaryOperator}} overload stays for method references and Java 
callers.
* {{CombinerChecker}} (GROOVY-12013) leaves a one-parameter closure alone: it 
is not a combiner.
* core-parallel-collections.adoc and the GPars migration table show the three 
forms.

Found while scoring Groovy 6.0.0 code written by language models: with the 
parallel-collections skill text in front of it, GPT-6 still wrote the 
one-parameter form.

  was:
{{Collection.sum()}} adds the elements, and {{sum(Closure)}} adds the 
transformed elements. {{ParallelCollectionExtensions.sumParallel(Collection<T>, 
BinaryOperator<T>)}} is a reduction with a required two-argument combiner 
(GPars' {{sumParallel()}} took no argument; the migration guide maps it to 
{{sumParallel \{ a, b -> a + b \}}} and notes that the accumulator is 
required). Code written by analogy with {{sum}} fails:

{code:groovy}
@CompileStatic
int total(List<Integer> numbers) {
    numbers.sumParallel { Integer n -> n }
}
{code}

{noformat}
[Static type checking] - Wrong number of parameters for method target: 
apply(java.lang.Integer, java.lang.Integer)
{noformat}

and in dynamic code {{items.sumParallel \{ it.price \}}} calls the 
one-parameter closure with two arguments.

Proposal, additive:
* {{sumParallel(Collection<?> self)}}: the elements added with the left 
operand's {{plus}}, as {{sum()}} does; an empty collection gives null.
* {{<T, R> R sumParallel(Collection<T> self, Closure<R> closure)}} with 
{{@ClosureParams(value = FromString, options = ["T", "T,T"])}}: a one-parameter 
closure is a transform and the transformed elements are added, the 
{{sum(Closure)}} contract; a two-parameter closure stays the combiner, so 
existing calls keep working and, under static compilation, keep their result 
type. The {{BinaryOperator}} overload stays for method references and Java 
callers.
* {{CombinerChecker}} (GROOVY-12013) leaves a one-parameter closure alone: it 
is not a combiner.
* core-parallel-collections.adoc and the GPars migration table show the three 
forms.

Found while scoring Groovy 6.0.0 code written by language models: with the 
parallel-collections skill text in front of it, GPT-6 still wrote the 
one-parameter form.


> sumParallel: add the no-argument and transform forms of sum(); the combiner 
> form reads as inject
> ------------------------------------------------------------------------------------------------
>
>                 Key: GROOVY-12722
>                 URL: https://issues.apache.org/jira/browse/GROOVY-12722
>             Project: Groovy
>          Issue Type: Improvement
>    Affects Versions: 6.0.0
>            Reporter: Scott Murphy Heiberg
>            Priority: Major
>
> {{Collection.sum()}} adds the elements, and {{sum(Closure)}} adds the 
> transformed elements. 
> {{ParallelCollectionExtensions.sumParallel(Collection<T>, 
> BinaryOperator<T>)}} is a reduction with a required two-argument combiner 
> (GPars' {{sumParallel()}} took no argument; the migration guide maps it to 
> the two-parameter closure form, sumParallel { a, b -> a + b }, and notes that 
> the accumulator is required). Code written by analogy with {{sum}} fails:
> {code:groovy}
> @CompileStatic
> int total(List<Integer> numbers) {
>     numbers.sumParallel { Integer n -> n }
> }
> {code}
> {noformat}
> [Static type checking] - Wrong number of parameters for method target: 
> apply(java.lang.Integer, java.lang.Integer)
> {noformat}
> and in dynamic code items.sumParallel { it.price } calls the one-parameter 
> closure with two arguments.
> Proposal, additive:
> * {{sumParallel(Collection<?> self)}}: the elements added with the left 
> operand's {{plus}}, as {{sum()}} does; an empty collection gives null.
> * {{<T, R> R sumParallel(Collection<T> self, Closure<R> closure)}} with 
> {{@ClosureParams(value = FromString, options = ["T", "T,T"])}}: a 
> one-parameter closure is a transform and the transformed elements are added, 
> the {{sum(Closure)}} contract; a two-parameter closure stays the combiner, so 
> existing calls keep working and, under static compilation, keep their result 
> type. The {{BinaryOperator}} overload stays for method references and Java 
> callers.
> * {{CombinerChecker}} (GROOVY-12013) leaves a one-parameter closure alone: it 
> is not a combiner.
> * core-parallel-collections.adoc and the GPars migration table show the three 
> forms.
> Found while scoring Groovy 6.0.0 code written by language models: with the 
> parallel-collections skill text in front of it, GPT-6 still wrote the 
> one-parameter form.



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