is there a simple way to window a `Sequence` based...

# stdlib

[mkobit]

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

[Shawn]

I don’t think there’s a simple way

[mkobit]

hah, kind of figured.

[Shawn]

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

[louiscad]

Can't fold do this?

[elizarov]

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)
}

[mkobit]

@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!