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https://issues.apache.org/jira/browse/GROOVY-11606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17942063#comment-17942063
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Paul King commented on GROOVY-11606:
------------------------------------
For the draft implementation, I have followed the Groovy-stream approach of
setting the delegate.
It means we can have code like this \(*):
{code:groovy}
var letters = Iterators.iterate('a', String::next)
var numbers = Iterators.iterate(0, Integer::next)
assert Iterators.combineLazy(true, x:letters, y:numbers)
.collectLazy{ x + y } // <<<===== (*)
.take(8)
.join(' ') == 'a0 a1 b0 b1 a2 b2 c0 c1'
{code}
Instead of this:
{code:groovy}
var letters = Iterators.iterate('a', String::next)
var numbers = Iterators.iterate(0, Integer::next)
assert Iterators.combineLazy(true, x:letters, y:numbers)
.map{ it.x + it.y } // <<<===== (*)
.take(8)
.join(' ') == 'a0 a1 b0 b1 a2 b2 c0 c1'
{code}
Another example:
{code:groovy}
assert [
[a:3, b:4, c:5],
[a:5, b:12, c:13],
[a:8, b:15, c:17],
[a:7, b:24, c:25]
].iterator().collectLazy {
c == Math.sqrt(a ** 2 + b ** 2)
}.join(' ') == 'true true true true'
{code}
An alternative using "with":
{code:groovy}
assert [
[a:3, b:4, c:5],
[a:5, b:12, c:13],
[a:8, b:15, c:17],
[a:7, b:24, c:25]
].iterator().map {
it.with {
c == Math.sqrt(a ** 2 + b ** 2)
}
}.join(' ') == 'true true true true'
{code}
An example with "findAllLazy":
{code:groovy}
assert [
[a:1, b:2, c:3],
[a:5, b:15, c:10],
[a:10, b:20, c:30]
].iterator().findAllLazy {
a + b == c
}.join(' ') == '[a:1, b:2, c:3] [a:10, b:20, c:30]'
{code}
Using "filter":
{code:groovy}
assert [
[a:1, b:2, c:3],
[a:5, b:15, c:10],
[a:10, b:20, c:30]
].iterator().filter {
it.a + it.b == it.c
}.join(' ') == '[a:1, b:2, c:3] [a:10, b:20, c:30]'
{code}
> Lazy findAll, collect, collectMany
> ----------------------------------
>
> Key: GROOVY-11606
> URL: https://issues.apache.org/jira/browse/GROOVY-11606
> Project: Groovy
> Issue Type: Improvement
> Reporter: Paul King
> Assignee: Paul King
> Priority: Major
>
> See:
> https://lists.apache.org/thread/xv1bpgc7xp3rwp7qt627xfyd10ljcwbc
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