CODEWITHSUNDEEP
scala
rasthiya
rasthiya

Reputation: 710

Update variables using multiple values returned from a function in Scala

Assume I have a function that return multiple values in scala.

def foo:(Double, Double) = {
    (1.1, 2.2)
}

I can call it as below without a problem.

val bar = foo

or

val (x, y) = foo

However, if I try to update existing variables like below, it doesn't work.

var x = 1.0
var y = 2.0
(x, y) = foo

This returns an error saying error: ';' expected but '=' found

Is there any reason behind this. Why can't I update the existing variables using (x, y) = foo

Upvotes: 2

Views: 512

Answers (1)

Tim
Tim

Reputation: 27356

The syntax for multiple assignment is actually an example of pattern matching. So this

val (x, y) = foo
...

is sort of equivalent to 

foo match {
  case (x, y) =>
    ...

This means that you can use more advanced pattern matching syntax like this:

val f @ (x, y) = foo

or this

val (x, _) = foo

But pattern matching can only be used to extract values into new variables, it can't be used to update existing variables, which is why the last bit of code does not compile. Scala code tends to avoid var anyway, so this is not a major problem for most programs.

Upvotes: 3

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