hello i have a list of numbers in the range 1-255....

# getting-started

[Moritz Post]

hello i have a list of numbers in the range 1-255. how could i transform these numbers into a ByteArray ? a direct conversion via byteArrayOf does not work since the numbers are unsigned but ubyteArrayOf does also not work for a reason i don't fully understand. It would be possible to map each number to it - 128 but that seams a bit unefficient. Help would be appreciated.

[Klitos Kyriacou]

The following will transform into a byteArray such that values between 128 and 255 will be negative (using 2's complement):

val list = listOf(0, 1, 80, 127, 128, 255, 256)
    val bytes = list.map { it.toByte() }.toByteArray()
    println(bytes.contentToString())

[Moritz Post]

thanks for the answer. that is a valid option.

[Paul Griffith]

val bytes = ByteArray(list.size) { list[it].toByte() }

is probably more efficient than the above; the ByteArray() pseudo-constructor is treated specially by the compiler

[Klitos Kyriacou]

Indeed. Assuming it's a random-access list, of course.