Scala, iterating a collection, working out 10% points - scala

Question

While iterating an arbitrarily-sized List, I'd like to print some output at ~10% intervals to show that the iteration is progressing. For any list of 10 or more elements, I want 10 outputs printed.
I've played around with % and Math functions, but am not always getting 10 outputs printed unless the list sizes are multiples of 10. Would appreciate your help.

Answer 1

One possibility is to calculate 10% of the size based on your input, and then use IterableLike.grouped to group based on that percent:
object Test {
def main(args: Array[String]): Unit = {
val range = 0 to Math.abs(Random.nextInt(100))
val length = range.length
val percent = Math.ceil((10.0 * length) / 100.0).toInt
println(s"Printing by $percent percent")
range.grouped(percent).foreach {
listByPercent =>
println(s"Printing $percent elements: ")
listByPercent.foreach(println)
}
}
}

Answer 2

Unless the length of your list is divisible by 10, then you are not going to get 10 print statements. Here I am rounding by interval up (ceil) so you will have less print statements. You could used Math.floor which would round down, and give you more print statements.
// Some list
val list = List.range(0, 27)
// Find the interval that is roughly 10 percent
val interval = Math.ceil(list.length / 10.0)
// Zip the list with the index, so that we can look at the indexes
list.zipWithIndex.foreach {
case (value, index) =>
// If an index is divisible by out interval, do your logging
if (index % interval == 0) {
println(s"$index / ${list.length}")
}
// Do something with the value here
}
Output:
0 / 27
3 / 27
6 / 27
9 / 27
12 / 27
15 / 27
18 / 27
21 / 27
24 / 27