Accumulates elements in iteration order, passing the current result and each element to operation. Returns initial unchanged when this iterable is empty.

forEach

inline fun <T> Iterable<T>.forEach(action: (T) -> Unit)

Calls action for each element in iteration order.

forEachIndexed

inline fun <T> Iterable<T>.forEachIndexed(action: (Int, T) -> Unit)

Calls action for each element and its zero-based index in iteration order.

indexOf

fun <T> Iterable<T>.indexOf(element: T): Int

Returns the index of the first equal element, or -1 when no element matches.

isEmpty

abstract fun isEmpty(): Boolean

isNotEmpty

fun <T> Collection<T>.isNotEmpty(): Boolean

Checks whether this collection has at least one element.

iterator

abstract operator fun iterator(): Iterator<T>

lastIndexOf

fun <T> Iterable<T>.lastIndexOf(element: T): Int

Returns the index of the last equal element, or -1 when no element matches.

lastOrNull

fun <T> Iterable<T>.lastOrNull(): T?

Returns the last element, or null when this iterable is empty.

inline fun <T> Iterable<T>.lastOrNull(predicate: (T) -> Boolean): T?

Returns the last matching element after traversing this iterable in iteration order.

map

inline fun <T, R> Collection<T>.map(transform: (T) -> R): List<R>

Maps a collection in iteration order, reserving its known size for the result.

inline fun <T, R> Iterable<T>.map(transform: (T) -> R): List<R>

Returns a list containing transform applied once to each element in iteration order.

mapNotNull

inline fun <T, R : Any> Iterable<T>.mapNotNull(transform: (T) -> R?): List<R>

Applies transform once per element in iteration order and retains only non-null results.

mapNotNullTo

inline fun <T, R : Any, C : MutableCollection<in R>> Iterable<T>.mapNotNullTo(destination: C, transform: (T) -> R?): C

Appends non-null transformed elements to destination and returns that destination.

mapTo

inline fun <T, R, C : MutableCollection<in R>> Iterable<T>.mapTo(destination: C, transform: (T) -> R): C

Appends transformed elements to destination in iteration order and returns that destination.

none

inline fun <T> Iterable<T>.none(predicate: (T) -> Boolean): Boolean

Returns true when no element matches predicate.

removeAll

abstract fun removeAll(p0: Collection<*>?): Boolean

retainAll

abstract fun retainAll(p0: Collection<*>?): Boolean