mapIndexed {i, v -> IndexedValue(i, v)}

.withIndex()

@Suppress("UNCHECKED_CAST")
fun <R> Iterable<*>.filterIsInstanceIndexed(clazz: Class<R>): List<IndexedValue<R>> =
  withIndex().filter { clazz.isInstance(it.value) } as List<IndexedValue<R>>

clazz

R

@Suppress("UNCHECKED_CAST")
inline fun <reified R: Any> Iterable<*>.filterIsInstanceIndexed(): List<IndexedValue<R>> =
  withIndex().filter { it.value is R } as List<IndexedValue<R>>

filterIsInstance

lateinit val

lateinit val

init

Map<K, List<V>>

Multimap

fun <K, V> MutableMap<K, MutableList<V>>.put(key: K, value: V) = getOrPut(key, { mutableListOf() }).add(value)

data class DataPoint(val date: ZonedDateTime, val value: Int): ToInt by value

reduce