Creating a matrix with values in Kotlin in convenience-CodePudding

I want to create the following one with a fancy notation:

arrayOf(intArrayOf(4, 5), intArrayOf(5, 8), intArrayOf(1, 9), intArrayOf(8, 10), intArrayOf(1, 6))

at least, cannot I achieve something that looks as follows:

arrayOf<IntArray>((4, 5), (5, 8), (1, 9), (8, 10), (1, 6))

because it is pretty awkward to rewrite intArrayOf for each row to put in.

Note that I do not ask for the following syntax I'm aware of which is used to initialize an empty matrix with values that are either same or following a common pattern.

val array = Array(row) { IntArray(column) }

CodePudding user response：

val result = listOf(4, 5, 5, 8, 1, 9, 8, 10, 1, 6)
  .chunked(2)
  .map { it.toIntArray() }
  .toTypedArray()

Edit 1:

The calculation could go into an extension function:

fun List<Int>.toArrayOfIntArrays() = this.chunked(2).map { it.toIntArray() }.toTypedArray()

val result = listOf(4, 5, 5, 8, 1, 9, 8, 10, 1, 6).toArrayOfIntArrays()

Edit 2:

Another option – assuming that the inner IntArrays all will consist of exactly two elements – would be to use a user-defined infix function:

infix fun Int.with(i1: Int) = intArrayOf(this, i1)

val result = arrayOf(4 with 5, 5 with 8, 1 with 9, 8 with 10, 1 with 6)

Any word not in conflict with the Kotlin keywords could be used, 'with' is just an example.

CodePudding user response：

If you simply don't like the wordiness of using intArrayOf you could define a shorter name to do the same, for example

fun i(vararg e: Int) = intArrayOf(*e)

And then do

arrayOf(i(4, 5), i(5, 8), i(1, 9), i(8, 10), i(1, 6))

CodePudding user response：

Here is my solution, abusing operator overloading ;)

object Matrix {
    operator fun get(vararg rows: IntArray) = rows
    operator fun get(vararg values: Int): IntArray = intArrayOf(*values)
}

fun main() {
    val result = Matrix.let { 
        it[
            it[1, 2, 3],
            it[4, 5, 6],
            it[7, 8, 9],
        ]
    }
    
    println(result.toList().map { it.toList() }) // [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
}

~~Please don't use it~~