In Kotlin, how can I take the first n elements of an array

Question

In Kotlin, how can I take the first n elements of this array:

val allColours = arrayOf(     Pair(Color.RED, Color.WHITE),      Pair(Color.RED, Color.BLACK),      Pair(Color.YELLOW, Color.BLACK),      Pair(Color.GREEN, Color.WHITE),      Pair(Color.BLUE, Color.WHITE),      Pair(Color.BLUE, Color.WHITE),      Pair(Color.CYAN, Color.BLACK),      Pair(Color.WHITE, Color.BLACK)) 

So how can I fill pegColours with the first say 3 Pairs?

var pegColours: Array<Pair<Color,Color>> = //??? 

I tried allColours.take but it gave an error:

Expecting an element

Answer 1

The problem with your code that you create pairs with color constants which are Ints (allColours has type Array<Pair<Int, Int>>), but you expect Array<Pair<Color, Color>>. What you have to do is change type pegColours type and use take:

var pegColours: Array<Pair<Int, Int>> = allColours.take(3).toTypedArray()  

Also you have to call toTypedArray() cause Array.take returns List rather than Array. Or you can change pegColours type as following:

var pegColours: List<Pair<Int, Int>> = allColours.take(3) 

Answer 2

You need to specify the number of items you want to take.

allColours.take(3) 

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For a random number of random indices, you can use the following:

val indexes = arrayOf(2, 4, 6) allColours.filterIndexed { index, s -> indexes.contains(index) } 

Note that you can write an extension method for this:

fun <T> Array<T>.filterByIndices(vararg indices: Int) = filterIndexed { index, _ -> indices.contains(index) } 

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Alternatively, if the indices are consecutive, you can use slice:

allColours.slice(1..3)