Multi-dimensonal arrays are a pain point in Kotlin

1

I love so much about Kotlin, but I have found one area where Java is actually friendlier to work with: mutli-dimensional arrays.

Not just in terms of verbosity, but I Think the readability is better in Java.

example:

Java:
int points = new int[10][10];

Kotlin:
val points = Array<Array<Int>>()

at two dimensionals it is managable, but at three or four I think it would be quite ugly.

Or is it possible I have missed a better way to do this?

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2

Could you share your use cases

3

The simplest use case is a 2d array to represent a grid for a tile based game.

It is not a big deal, but everything else about Kotlin is so nice this jumps out at me.

4

Ok, thanks

5

Have you considered adding Ceylon style type aliases? Would solve this problem.

6

Yes, we are planning to support something like this

1 Like
7

I think, this works. I have tried it in a Scratch file:

val d2 = arrayOf( Array(255,{i → i-1+1}), Array(255,{i → i-1+1}) )

d2[0][1]

And i think, it is no problem to make 3 dimensional Arrays.

8

You should track this issue: https://youtrack.jetbrains.com/issue/KT-21670. Multi-dimensional arrays are not that simple. Java arrays are quite easy to use, but are not what you need in terms of performance. Lightweight 2-dim array builders are quite easy to add in you project like this:

typealias DoubleArray2D = Array<DoubleArray>
fun doubleArray2D(rows: Int, cols: Int, block: (i: Int, j: Int) -> Double): DoubleArray2D{
  return Array(rows){ i ->
      DoubleArray(cols){ j ->
          block(i,j)
      }
  }
}
1 Like