Question

I have a 2d array of type boolean (not important)
It is easy to iterate over the array in non-functional style.
How to do it FP style?

var matrix = Array.ofDim[Boolean](5, 5) 

for ex, I would like to iterate through all the rows for a given column and return a list of int that would match a specific function.
Example: for column 3, iterate through rows 1 to 5 to return 4, 5 if the cell at (4, 3), (5, 3) match a specif function. Thx v much

def getChildren(nodeId: Int) : List[Int] = {
    info("getChildren("+nodeId+")")

    var list = List[Int]()
    val nodeIndex = id2indexMap(nodeId)

    for (rowIndex <- 0 until matrix.size) {
      val elem = matrix(rowIndex)(nodeIndex)
      if (elem) {
        println("Row Index = " + rowIndex)
        list = rowIndex :: list
      }
    }

    list
  }

Answer 1

What about

(1 to 5) filter {i => predicate(matrix(i)(3))}

where predicate is your function?

Note that initialized with (5,5) indexes goes from 0 to 4.

Update: based on your example

def getChildren(nodeId: Int) : List[Int] = {
  info("getChildren("+nodeId+")")
  val nodeIndex = id2indexMap(nodeId)

  val result = (0  until matrix.size).filter(matrix(_)(nodeIndex)).toList
  result.forEach(println)
  result
}

You may move the print in the fiter if you want too, and reverse the list if you want it exactly as in your example