given starting point

val start = 0

and

listOf(3, 3, 3, 2)

representing sizes of IntRange’s, whats the simplest way to turn this into a list of IntRanges? expected outcome

listOf(IntRange(0, 2), IntRange(3, 5), IntRange(6, 8), IntRange(9, 10))

I'd just go for a straightforward for loop inside a generator sequence:

val start = 0
val list = listOf(3, 3, 3, 2)
val seq = sequence {
    var curr = start
    for (el in list) {
        val next = curr + el
        yield(curr until next)
        curr = next
    }
}

let me try this 🙂

My $0.02:

val sizes = listOf(3, 3, 3, 2)
    var start = 0
    val ranges = sizes.map { size -> IntRange(start, start + size - 1).also {
            start += size
        }
    }

Personally not a fan of mutating state inside

map

and friends tbh

Me neither

works, thanks guys

val start = 0
val list = listOf(3, 3, 3, 2)

val listNew = list.drop(1).fold(listOf(IntRange(start, list.first() - 1))) { acc, v ->
    val r = acc.last().last
    acc + listOf(IntRange(r + 1, r + v))
}
println(listNew)

But I'd recommend use simple for loop instead, since it's easier to read and understand

Another functional (thus not very effective) approach:

val ranges = sizes
    .fold(listOf(start)) { stops, length -> stops + (stops.last() + length) }
    .zipWithNext { s, e -> s until e }

https://pl.kotl.in/SJrwLstRQ

wow, thanks for all suggestions