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In limited sense it is very easy to write out and ref classes on your own, but my question is not how to do it — but are there some features (or classes) ready to use?
The closest thing I found is Reference trait (but it is a trait).
I need those, not tuple, not Option, and not Either as pure result, because only ref/out makes chaining ifs elegant.
No, Scala supports parameter passing by value or by name. Parameter passing by reference is actually quite difficult to accomplish correctly in the JVM, which is probably one reason why none of the popular JVM languages have it. Additionally, out and ref parameters encourage programming via side-effect, something the at design of Scala attempts to avoid wherever possible.
As for chaining of if’s, there are a variety of ways to achieve some effects like that in Scala. “match” expressions are the most obvious, and you might also look into monadic compositions using Option or Either.