Hi folks,
JDK24 brought with it the Gatherers API for enhanced stream processing.
In traditional streams, we have the normal reduce operators, e.g.:
var nums = 1..3
assert nums.stream().reduce('', (String string, number) -> string +
number) == '123'
Groovy supports this for collections using "inject":
assert nums.inject(''){ carry, next -> carry + next } == '123'
But now there is also the prefix sum variant "scan", which I am told
has a myriad of uses, though I don't commonly use it myself. Note it
has the same reduce function as above:
assert nums.stream()
.gather(Gatherers.scan(() -> '', (string, number) -> string + number))
.toList() == ['1', '12', '123']
We can also emulate this for collections (with a little ugliness)
using the vanilla inject:
assert nums.inject([]) { sum, next ->
[*sum, "${sum.takeRight(1)[0] ?: ''}$next"]
} == ['1', '12', '123']
I am wondering whether we could actually provide the same
functionality as scan above, something like this (name "injectMany"
currently but open to a better name):
assert nums.injectMany(''){ carry, next -> carry + next } == ['1', '12', '123']
It is only a minor change to the inject code, so not a huge technical
challenge, but what do folks think? Should we round out our collection
support to provide similar functionality to that available in streams?
Regards,
Paul.
