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#java

00:51 acidjnk nvm, extract that one method, and it's fine
01:15 jreicher acidjnk: I'm not sure syntax is your problem there. Why are you flatmapping onto a lambda that produces a stream?
11:16 acidjnk the logic is correct jreicher, but it shows that readability is not good enough yet, although I also did not provide all the context. I ended up making this utility method, surprised that it did not exist in the core API yet. It's like zip, but cartesian instead of pair-wise: https://pastebin.com/UxGdLa8t
11:52 dreamreal acidjnk: what id this trying to do?
11:56 acidjnk What I'm using it for is a JUnit DynamicTest and @TestFactory. I have a list of first arguments, a list of second arguments, and need to call a parameterized test with all possible combinations. Some JUnit library has a @Cartesian annotation or something like that with similar effect.
11:56 Para Cartesian product as a stream assumes extrapolating a two-dimensional result from a sequence. That's not very generalizable -> no method in API.
11:57 Para As a group of operations that's zip + reduce, though. I don't think n-stream zipper exists in core API either.
11:58 Para (per dimension)
11:58 dreamreal para's right, I actually use a set of nested values in a methodsource to do it: for(var v1 :setOfV1s) { for(var v2: setofV2) { ... compose set here } }
11:58 Para this guy's done a pretty good zipping gatherer https://www.morling.dev/blog/zipping-gatherer/
11:58 javabot Para's title: "A Zipping Gatherer - Gunnar Morling"
11:59 Para Hm, I think I've seen this SO post before :) https://stackoverflow.com/questions/17640754/zipping-streams-using-jdk8-with-lambda-java-util-stream-streams-zip
11:59 javabot Para's title: "functional programming - Zipping streams using JDK8 with lambda (java.util.stream.Streams.zip) - Stack Overflow"
11:59 acidjnk jOOλ has something similar, but as two calls. It has a crossjoin to create the tuples, and then it's just mapping to a BiFunction. I was considering to just use that as a library.
11:59 * dreamreal shrugs. Do what works for you.
12:02 acidjnk when you can use methodsource, @CartesianTest would also work: https://junit-pioneer.org/docs/cartesian-product/ Mine can't use method source, because it is abstract, and I need the elements defined by the corresponding implementations.
12:02 nevet Cartesian Product of Parameters
12:03 dreamreal oooo I need to look at that, I've been doing it manually
12:03 dreamreal I keep thinking junit's just not all that flexible, people keep adding it.
12:04 dreamreal oh, of course, that's not junit proper, that's why
12:04 acidjnk yes. I looked at all sorts of alternatives before I resorted to @TestFactory
12:36 jreicher acidjnk: I never said the logic was wrong. I'm asking why you've chosen to implement it using this combination of operations.
12:55 acidjnk Reasonable question, but from the question itself I concluded: Ok, it's not obvious that I want to call a method with all possible combinations of the elements from the two sources.