Let’s say, I have the following code snippet:
val num = Future.successful(10)
num map {
case n if n > 0 => // do something
case _ // do something
}
My question is: can I simplify case n if n > 0 somehow?
I expected that I can write something like:
case _ > 0 => // do something
or with explicitly specified type (although we know that Future has inferred type [Int]):
case _: Int > 0 => // do something
Can this code be simplified somehow?
If not, is it possible to introduce such feature in newer Scala versions?
Yes, it’s possible to define a custom pattern matcher so you can say:
case Positive(n) => ...
You would do this by writing a Positive object with an unapply method that checks and returns Some n if n is positive and None otherwise.
Thank you. Seems to be very interesting. Remains only to convince my team 
Personally I wouldn’t do this, case n if n ... => ... is simple enough and still pretty elegant 
1 Like
czeng
5
Wow! Really a good and interesting idea! Though it might be hard to
maintain. LOL
If you like underscores, here’s a fun one.
num map (_ > 0) map (if(_) "ok" else "nok")
That seems to work how I’d expect, although you could also use operator sectioning to make it even more fun:
num map (0.<) map (if (_) "ok" else "nok")
