Is there a way to initialize multiple variables from array or List in Scala?

Question

What I want to do is basically the following in Java code:

String[] tempStrs = generateStrings();
final int hour = Integer.parseInt(tempStrs[0]);
final int minute = Integer.parseInt(tempStrs[1]);
final int second = Integer.parseInt(tempStrs[2]);

However, tempStrs is just a temporary variable, which is not used anymore. Then, this can be expressed in the following code in F#:

let [| hour; minute; second |] = Array.map (fun x -> Int32.Parse(x)) (generateStrings())

Is there a similar way to do this in Scala? I know this can be done in Scala by

val tempInts = generateStrings().map(_.toInt)
val hour = tempInts(0)
val minute = tempInts(1)
val second = tempInts(2)

But is there a shorter way like F# (without temp variable)?

Edit:

I used

var Array(hour, minute, second) = generateStrings().map(_.toInt)

Of course, using val instead of var also worked.

sberry · Accepted Answer · 2013-08-19 06:19:07Z

23

How about this:

scala> val numbers = List(1, 2, 3)
numbers: List[Int] = List(1, 2, 3)

scala> val List(hours, minutes, seconds) = numbers
hours: Int = 1
minutes: Int = 2
seconds: Int = 3

answered Aug 19, 2013 at 6:19

sberry

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4 Comments

Sebastien Lorber Over a year ago

nice, but it seems to produce matcherror if the list doesn't have size 3.

om-nom-nom Over a year ago

@SebastienLorber val List(hours, minutes, seconds, _*)

Sebastien Lorber Over a year ago

@om-nom-nom that's right but it only works when size > 3 no? I think it works fine but can be dangerous to use in some situations

om-nom-nom Over a year ago

@SebastienLorber no it should be fine in case of 3 values: val List(hours, minutes, seconds, _*) = List(1,2,3) will compile and execute effortlessly. It will only fail in case of less than 3 which is pretty desired behaviour.

Shadowlands · Accepted Answer · 2013-08-19 10:13:11Z

4

To deal with three or more values, you could use:

scala> val numbers = List(1, 2, 3, 4)
numbers: List[Int] = List(1, 2, 3, 4)

scala> val num1 :: num2 :: num3 :: theRest = numbers
num1: Int = 1
num2: Int = 2
num3: Int = 3
theRest: List[Int] = List(4)

For a size-3 list theRest will simply be the empty list. Of course, it doesn't handle lists of two or fewer elements.

answered Aug 19, 2013 at 10:13

Shadowlands

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