CODEWITHSUNDEEP
scala
user1868607
user1868607

Reputation: 2610

Accessing list of lists inside a for

I have the following bit of code in scala which is not working:

 var tacTable : List[List[TACList]] = List(List())

  def gen(p: Program) = {
    for (i <- 0 to p.classes.length){
      for (j <- 0 to p.classes(i).methods.length){
        var tacInstr = new TACList()
        tacTable(i)(j) = tacInstr //error: application does not take parameters
      }
    }
  }

Apparently, it has to do with the fact that I'm using j to access the list and j is used in for...how can I solve this?

For convenience you can work with this other example which gives the same error:

var l : List[List[Int]] = List(List(1,2),List(3,4))
for (i <- 0 to l.length) {
  for (j <- 0 to l.length) {
    l(i)(j) = 8
  }
}

Upvotes: 0

Views: 91

Answers (2)

winson
winson

Reputation: 428

since I cannot comment on the initial post a sidenote here:

in a scala for-comprehension you can use multiple generators in a single for. so the nesting that you used is not necessary since you can use this:

for (i <- 0 to l.length; j <- 0 to l.length) {
  // your code
}

furthermore, this does not seem to apply in your case but if you had a flat mapped result you should use the yield of the for comprehension instead of a mutation in the body

Upvotes: 1

Dima
Dima

Reputation: 40508

Lists are immutable. Try this instead:

 val tacTable  = p.classes.map { _.methods.map { _ =>
     new TACList()
 }

Upvotes: 1

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