scala pattern matching nested cases

Question

I try to match after some case applied. Kind of nested cases/matches:

val x1 = 2 // or 1, 3 ...
val str = x1 match {   // scala.MatchError: 1 (of class java.lang.Integer)

  case x if(x > 1) => "x"+x match {case "x1" => "yes"}

  // updated:
  case _ => "nope"
}
println (str)

It fails with scala.MatchError exception.

Is it possible? It seems I've seen something similar.

Exception in thread "main" scala.MatchError: x2 (of class java.lang.String) at pattern_matching.PatternMatchingTest$delayedInit$body.apply(PatternMatchingTest.scala:32) at scala.Function0$class.apply$mcV$sp(Function0.scala:40) at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12) at scala.App$$anonfun$main$1.apply(App.scala:71) at scala.App$$anonfun$main$1.apply

Shadowlands · Accepted Answer · 2013-09-09 23:57:51Z

4

The problem you are hitting is that your example input (val x1 = 1) doesn't match the one case you gave (since x1 is not greater than 1). You will need to either modify your existing case (eg. change the if to something like if(x >= 1)) or add at least one more case, and should probably consider a default case. eg.:

val str = x1 match {   // scala.MatchError: 1 (of class java.lang.Integer)
  case x if(x > 1) => "x"+x match {case "x1" => "yes"}
  case _ => "no match"
}

answered Sep 9, 2013 at 23:57

Shadowlands

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3 Comments

ses Over a year ago

even if 2 (just was experimenting)

Shadowlands Over a year ago

Yes, because now you fail in the second match ("x2" != "x1")

ses Over a year ago

Hm.. strange it managed get success after second compile. At least I glad that it works like I expected in terms of syntax.

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