If I want to have two loops to iterate an array of Int values (to compare them to each other), but I...

# getting-started

[Colton Idle]

If I want to have two loops to iterate an array of Int values (to compare them to each other), but I want the inner loop always start at outerIndex++, how would I do that?

Currently I have

array.forEachIndexed { indexOuter, outer ->
        array.forEachIndexed { indexInnter, inner ->
            //I want this inner forEachIndexed to start at indexOuter++
        }
    }

[Colton Idle]

I thought maybe the inner would be able to do something java-esque like this:

for (val indexInner = indexOuter++, indexInner < array.size, indexInner++){
//inner loop stuff
}

[Josh Eldridge]

for (i in 1..3) {
    println(i)
}

[Josh Eldridge]

You can use that as the inner loop and start the range with the outer index and end with the length of the inner array

[Josh Eldridge]

https://kotlinlang.org/docs/control-flow.html#for-loops

[Colton Idle]

Why does something like this not work?

for (outer in array.size){
        println("$outer and ${array[outer]}")
}

[Colton Idle]

I guess im just lost in the kotlin for loop syntax.

[Colton Idle]

i think im holding onto java patterns a bit too much

[Colton Idle]

I ended up with this though. Thanks for the sanity check @Josh Eldridge

for (outer in 0 until array.size) {
        for (inner in outer + 1 until array.size) {
            //do stuff with array[outer] and array[inner]
        }
    }

[Josh Eldridge]

The kotlin devs decided to use a different syntax I guess 🤷, glad I could help

[Luke Armitage]

not tried this in an REPL or anything, but off the top of my head something like this should work:

array.forEachIndexed { idx, outer ->
    array.drop(idx + 1).forEach { inner ->
        //  do stuff with inner and outer
    }
}

[Luke Armitage]

probably got an off-by-one error in the drop(idx + 1) there....

[Francesc]

If you are looping over a full collection, you can use indices instead of manually specifying the range

[Francesc]

https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/indices.html

[Francesc]

for (outer in array.indices)