Pattern matching with regexes in Scala

Question

Why doesn't this work?

val isGovt = """Govt .*""".r
val Govt = "Govt 23 foobar"
Govt match {
    case isGovt(_) => println("match works")
    case _ => print("nope. doesn't work")
}

It prints 'nope. doesn't work'. What am I doing wrong?

Régis Jean-Gilles · Accepted Answer · 2014-11-18 13:10:59Z

6

Change

val isGovt = """Govt .*""".r

to

val isGovt = """(Govt .*)""".r

When you use a regex as an extractor, the bound variables correspond to the regex's groups. Your regex had none.

You could also simply keep your regex as is and do:

case isGovt() =>

This is probably more like hat you had in mind.

edited Nov 18, 2014 at 13:10

answered Nov 18, 2014 at 13:05

Régis Jean-Gilles

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4 Comments

Sergii Lagutin Over a year ago

+1 Or change case isGovt(_) => println("match works") to case isGovt => println("match works")

Régis Jean-Gilles Over a year ago

You meant case isGovt() I guess. Added to my answer, thanks.

Core_Dumped Over a year ago

@RégisJean-Gilles What if I want to match something like this: """(Govt \\d.*)""".r ? This does not seem to work for say "Govt 23 foobar"

Régis Jean-Gilles Over a year ago

Your regex is wrong: you doubled the backslash but you should not because you are already using triple-quotes, which don't require escaping. Try """(Govt \d.*)""".r

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