How can I capture multiple variables using pattern matching?

Question

For example:

List(1,2,3,4) match {
  case List(x: Int, y: Int, *rest) =>
    println(rest) // i want to get List(3,4)
}

_* can match multiple variables but do to seem to be able to capture them.

Thanks!

List(1,2,3,4) match { case ele1 :: ele2 :: rest => {} }

sarveshseri
– sarveshseri

2016-08-03 09:19:36 +00:00
Commented Aug 3, 2016 at 9:19 — sarveshseri
– sarveshseri, Commented Aug 3, 2016 at 9:19

Alexey Romanov · Accepted Answer · 2016-08-03 09:41:17Z

4

You can use rest @ _* for this:

List(1,2,3,4) match {
  case List(x: Int, y: Int, rest @ _*) =>
    println(rest) 
}

Note that this is general: you can use x @ pattern to give the name x to any value matched by pattern (provided this value has a suitable type). See http://scala-lang.org/files/archive/spec/2.11/08-pattern-matching.html#pattern-binders.

edited Aug 3, 2016 at 9:41

answered Aug 3, 2016 at 9:35

Alexey Romanov

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Paweł Jurczenko · Accepted Answer · 2016-08-03 09:23:18Z

2

List(1, 2, 3, 4) match {
  case _ :: _ :: tail => println(tail) // prints List(3, 4)
}

answered Aug 3, 2016 at 9:23

Paweł Jurczenko

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Comments

Fellrond · Accepted Answer · 2016-08-03 09:25:27Z

2

You can simply match lists by cons operator:

List(1, 2, 3, 4) match { 
    case x :: y :: rest => println(rest) 
} // gives you "List(3, 4)" to stdout

answered Aug 3, 2016 at 9:25

Fellrond

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Comments

elm · Accepted Answer · 2016-08-03 10:12:05Z

1

Another way to invoke pattern matching on lists,

val List(x,y,rest @ _*) = List(1,2,3,4)

which extracts

x: Int = 1
y: Int = 2
rest: Seq[Int] = List(3, 4)

edited Aug 3, 2016 at 10:12

answered Aug 3, 2016 at 9:46

elm

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