Possible Duplicate:
Tuple parameter declaration and assignment oddity
In Scala, one can do multiple-variable assignment to tuples via:
val (a, b) = (1, 2)
But a similar syntax for assignment to variables doesn't appear to work. For example I'd like to do this:
var (c, d) = (3, 4)
(c, d) = (5, 6)
I'd like to reuse c and d in multiple-variable assignment. Is this possible?
This isn't simply "multiple variable assignment", it's fully-featured pattern matching!
So the following are all valid:
val (a, b) = (1, 2)
val Array(a, b) = Array(1, 2)
val h :: t = List(1, 2)
val List(a, Some(b)) = List(1, Option(2))
This is the way that pattern matching works, it'll de-construct something into smaller parts, and bind those parts to new names. As specified, pattern matching won't bind to pre-existing references, you'd have to do this yourself.
var x: Int = _
var y: Int = _
val (a, b) = (1, 2)
x = a
y = b
// or
(1,2) match {
case (a,b) => x = a; y = b
case _ =>
}
I don't think what you want is possible, but you can get something quite similar with the "magical" update method.
case class P(var x:Int, var y:Int) {
def update(xy:(Int, Int)) {
x = xy._1
y = xy._2
}
}
val p = P(1,2)
p() = (3,4)
