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 }

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