CODEWITHSUNDEEP
scalafor-loop
lolveley
lolveley

Reputation: 1709

Assignment of a var arraybuffer in a for loop : "reassignment to val"

As said in the title, I can't reassign a variable of type Arraybuffer(Arraybuffer(Int,Int),Int) in a for loop:

var ab1 = ArrayBuffer(le4: _*)
var ab2 = ab1 map (ligne => (ArrayBuffer(ligne._1: _*), ligne._2))
println("ab:" + ab2)

for {
    i <- 1 to ab2.length
    j <- 0 to i
} {
    ab2(i)._1(j)._2 = j match {
        case 0 =>  ab2(i - 1)._1(0)._2 + ab2(i)._1(j)._1
        case i =>  ab2(i - 1)._1(j - 1)._2 + ab2(i)._1(j)._1
        case _ =>  ab2(i - 1)._1(j)._2 + ab2(i - 1)._1(j - 1)._1 + ab2(i)._1(j)._1
    }
}

the key point is that ab2 is declared as var but the change of an Int inside it is denied. Why?

Upvotes: 1

Views: 960

Answers (1)

Dylan
Dylan

Reputation: 13922

There's a difference between a var, and a mutable object.

  • var can have its value reassigned at will
  • a mutable object can have its fields reassigned. Like an object with vars in it

You are trying to set the _2 field of a tuple inside of ab2; tuples are immutable, and that's why it causes a compiler error.

Reconsider the data structure you're using for this operation. A collection.mutable.Map might be better, or anything else that has an update method which allows you to change values inside of it.

Upvotes: 6

Related Questions