Why are functions like `.sumBy()` not defined on `...

# announcements

[Paul Woitaschek]

Why are functions like .sumBy() not defined on kotlin.collections.Iterator<T> too?
I'm using android-ktx fun <T> androidx.collection.SparseArrayCompat<T>.valueIterator(): kotlin.collections.Iterator<T> and would like to sum the values.
As a workaround I can call toSequence().sumBy { it }

[karelpeeters]

Because that's exactly what a sequence is: a wrapper around an iterator.

[karelpeeters]

Adding extra overloads for iterators would be confusing: would it be eager (like iterable) or lazy (like sequences)?