is there a simple way to window a

Sequence

based on attributes of the data? for example, if i have

sequenceOf(1,2,3,5,6,8,10,14,15)

i'd like to "merge" contiguous elements together into a sequence that is

sequenceOf([1,2,3], [5,6], [8], [10], [14,15])

i'd like to retain the lazy evaluation, such that

[1,2,3]

is yielded only when it is needed

I don’t think there’s a simple way

hah, kind of figured.

you could build a sequence that’s smart enough to read just enough of the data source to determine where to set the window boundaries, but afaik there isn’t like a simple pass-in-a-lambda solution in the stdlib

Can't

fold

do this?

Coroutines to the rescue:

fun Sequence<Int>.contiguous() = sequence<List<Int>> {
    val cur = mutableListOf<Int>()
    for (x in this@contiguous) {
        if (cur.isNotEmpty() && x != cur.last() + 1) {
            yield(cur.toList())
            cur.clear()
        }
        cur += x
    }
    if (cur.isNotEmpty()) yield(cur)
}

@Shawn good suggestion, that is essentially what i ended up doing @louiscad i think

fold

would be terminal and consume all of the elements (unless i'm missing something) @elizarov that's close to how i did it, except i used

Sequence.iterator

with

hasNext

as my looping condition i think your approach is cleaner, and im going to change mine to more closely follow your model thanks for the help everybody!