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Package kotlin.sequences

Sequence type that represents lazily evaluated collections. Top-level functions for instantiating sequences and extension functions for sequences.

Classification of sequences

The sequence operations can be classified into the following groups regarding their state requirements:

If the sequence operation returns another sequence, which is produced lazily, it's called intermediate, and otherwise the operation is terminal. Examples of terminal operations are kotlin.sequences.Sequence.toList, kotlin.sequences.Sequence.max.

Sequences can be iterated multiple times, however some sequence implementations might constrain themselves to be iterated only once. That is mentioned specifically in their documentation (e.g. kotlin.sequences.generateSequence overload). The latter sequences throw an exception on an attempt to iterate them the second time.

Types

Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

Sequence

A sequence that returns values through its iterator. The values are evaluated lazily, and the sequence is potentially infinite.

interface Sequence<out T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

SequenceBuilder

typealias SequenceBuilder<T> = SequenceScope<T>
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

SequenceScope

The scope for yielding values of a Sequence or an Iterator, provides yield and yieldAll suspension functions.

abstract class SequenceScope<in T>

Extensions for External Classes

Platform and version requirements: JVM (1.0)

java.util.Enumeration

Functions

Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

all

Returns true if all elements match the given predicate.

fun <T> Sequence<T>.all(predicate: (T) -> Boolean): Boolean
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

any

Returns true if sequence has at least one element.

fun <T> Sequence<T>.any(): Boolean

Returns true if at least one element matches the given predicate.

fun <T> Sequence<T>.any(predicate: (T) -> Boolean): Boolean
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

asIterable

Creates an Iterable instance that wraps the original sequence returning its elements when being iterated.

fun <T> Sequence<T>.asIterable(): Iterable<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

asSequence

Returns this sequence as a Sequence.

fun <T> Sequence<T>.asSequence(): Sequence<T>

Creates a sequence that returns all elements from this iterator. The sequence is constrained to be iterated only once.

fun <T> Iterator<T>.asSequence(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

associate

Returns a Map containing key-value pairs provided by transform function applied to elements of the given sequence.

fun <T, K, V> Sequence<T>.associate(
    transform: (T) -> Pair<K, V>
): Map<K, V>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

associateBy

Returns a Map containing the elements from the given sequence indexed by the key returned from keySelector function applied to each element.

fun <T, K> Sequence<T>.associateBy(
    keySelector: (T) -> K
): Map<K, T>

Returns a Map containing the values provided by valueTransform and indexed by keySelector functions applied to elements of the given sequence.

fun <T, K, V> Sequence<T>.associateBy(
    keySelector: (T) -> K, 
    valueTransform: (T) -> V
): Map<K, V>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

associateByTo

Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function applied to each element of the given sequence and value is the element itself.

fun <T, K, M : MutableMap<in K, in T>> Sequence<T>.associateByTo(
    destination: M, 
    keySelector: (T) -> K
): M

Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function and and value is provided by the valueTransform function applied to elements of the given sequence.

fun <T, K, V, M : MutableMap<in K, in V>> Sequence<T>.associateByTo(
    destination: M, 
    keySelector: (T) -> K, 
    valueTransform: (T) -> V
): M
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

associateTo

Populates and returns the destination mutable map with key-value pairs provided by transform function applied to each element of the given sequence.

fun <T, K, V, M : MutableMap<in K, in V>> Sequence<T>.associateTo(
    destination: M, 
    transform: (T) -> Pair<K, V>
): M
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

associateWith

Returns a Map where keys are elements from the given sequence and values are produced by the valueSelector function applied to each element.

fun <K, V> Sequence<K>.associateWith(
    valueSelector: (K) -> V
): Map<K, V>
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

associateWithTo

Populates and returns the destination mutable map with key-value pairs for each element of the given sequence, where key is the element itself and value is provided by the valueSelector function applied to that key.

fun <K, V, M : MutableMap<in K, in V>> Sequence<K>.associateWithTo(
    destination: M, 
    valueSelector: (K) -> V
): M
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

average

Returns an average value of elements in the sequence.

fun Sequence<Byte>.average(): Double
fun Sequence<Short>.average(): Double
fun Sequence<Int>.average(): Double
fun Sequence<Long>.average(): Double
fun Sequence<Float>.average(): Double
fun Sequence<Double>.average(): Double
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

buildIterator

fun <T> buildIterator(
    builderAction: suspend SequenceScope<T>.() -> Unit
): Iterator<T>
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

buildSequence

fun <T> buildSequence(
    builderAction: suspend SequenceScope<T>.() -> Unit
): Sequence<T>
Platform and version requirements: JVM (1.2), JS (1.2), Native (1.2)

chunked

Splits this sequence into a sequence of lists each not exceeding the given size.

fun <T> Sequence<T>.chunked(size: Int): Sequence<List<T>>

Splits this sequence into several lists each not exceeding the given size and applies the given transform function to an each.

fun <T, R> Sequence<T>.chunked(
    size: Int, 
    transform: (List<T>) -> R
): Sequence<R>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

constrainOnce

Returns a wrapper sequence that provides values of this sequence, but ensures it can be iterated only one time.

fun <T> Sequence<T>.constrainOnce(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

contains

Returns true if element is found in the sequence.

operator fun <T> Sequence<T>.contains(element: T): Boolean
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

count

Returns the number of elements in this sequence.

fun <T> Sequence<T>.count(): Int

Returns the number of elements matching the given predicate.

fun <T> Sequence<T>.count(predicate: (T) -> Boolean): Int
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

distinct

Returns a sequence containing only distinct elements from the given sequence.

fun <T> Sequence<T>.distinct(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

distinctBy

Returns a sequence containing only elements from the given sequence having distinct keys returned by the given selector function.

fun <T, K> Sequence<T>.distinctBy(
    selector: (T) -> K
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

drop

Returns a sequence containing all elements except first n elements.

fun <T> Sequence<T>.drop(n: Int): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

dropWhile

Returns a sequence containing all elements except first elements that satisfy the given predicate.

fun <T> Sequence<T>.dropWhile(
    predicate: (T) -> Boolean
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

elementAt

Returns an element at the given index or throws an IndexOutOfBoundsException if the index is out of bounds of this sequence.

fun <T> Sequence<T>.elementAt(index: Int): T
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

elementAtOrElse

Returns an element at the given index or the result of calling the defaultValue function if the index is out of bounds of this sequence.

fun <T> Sequence<T>.elementAtOrElse(
    index: Int, 
    defaultValue: (Int) -> T
): T
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

elementAtOrNull

Returns an element at the given index or null if the index is out of bounds of this sequence.

fun <T> Sequence<T>.elementAtOrNull(index: Int): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

emptySequence

Returns an empty sequence.

fun <T> emptySequence(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

filter

Returns a sequence containing only elements matching the given predicate.

fun <T> Sequence<T>.filter(
    predicate: (T) -> Boolean
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

filterIndexed

Returns a sequence containing only elements matching the given predicate.

fun <T> Sequence<T>.filterIndexed(
    predicate: (index: Int, T) -> Boolean
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

filterIndexedTo

Appends all elements matching the given predicate to the given destination.

fun <T, C : MutableCollection<in T>> Sequence<T>.filterIndexedTo(
    destination: C, 
    predicate: (index: Int, T) -> Boolean
): C

filterIsInstance

Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

Returns a sequence containing all elements that are instances of specified type parameter R.

fun <R> Sequence<*>.filterIsInstance(): Sequence<R>
Platform and version requirements: JVM (1.0)

Returns a sequence containing all elements that are instances of specified class.

fun <R> Sequence<*>.filterIsInstance(
    klass: Class<R>
): Sequence<R>

filterIsInstanceTo

Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

Appends all elements that are instances of specified type parameter R to the given destination.

fun <R, C : MutableCollection<in R>> Sequence<*>.filterIsInstanceTo(
    destination: C
): C
Platform and version requirements: JVM (1.0)

Appends all elements that are instances of specified class to the given destination.

fun <C : MutableCollection<in R>, R> Sequence<*>.filterIsInstanceTo(
    destination: C, 
    klass: Class<R>
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

filterNot

Returns a sequence containing all elements not matching the given predicate.

fun <T> Sequence<T>.filterNot(
    predicate: (T) -> Boolean
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

filterNotNull

Returns a sequence containing all elements that are not null.

fun <T : Any> Sequence<T?>.filterNotNull(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

filterNotNullTo

Appends all elements that are not null to the given destination.

fun <C : MutableCollection<in T>, T : Any> Sequence<T?>.filterNotNullTo(
    destination: C
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

filterNotTo

Appends all elements not matching the given predicate to the given destination.

fun <T, C : MutableCollection<in T>> Sequence<T>.filterNotTo(
    destination: C, 
    predicate: (T) -> Boolean
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

filterTo

Appends all elements matching the given predicate to the given destination.

fun <T, C : MutableCollection<in T>> Sequence<T>.filterTo(
    destination: C, 
    predicate: (T) -> Boolean
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

find

Returns the first element matching the given predicate, or null if no such element was found.

fun <T> Sequence<T>.find(predicate: (T) -> Boolean): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

findLast

Returns the last element matching the given predicate, or null if no such element was found.

fun <T> Sequence<T>.findLast(predicate: (T) -> Boolean): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

first

Returns first element.

fun <T> Sequence<T>.first(): T

Returns the first element matching the given predicate.

fun <T> Sequence<T>.first(predicate: (T) -> Boolean): T
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

firstOrNull

Returns the first element, or null if the sequence is empty.

fun <T> Sequence<T>.firstOrNull(): T?

Returns the first element matching the given predicate, or null if element was not found.

fun <T> Sequence<T>.firstOrNull(
    predicate: (T) -> Boolean
): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

flatMap

Returns a single sequence of all elements from results of transform function being invoked on each element of original sequence.

fun <T, R> Sequence<T>.flatMap(
    transform: (T) -> Iterable<R>
): Sequence<R>
fun <T, R> Sequence<T>.flatMap(
    transform: (T) -> Sequence<R>
): Sequence<R>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

flatMapIndexed

Returns a single sequence of all elements yielded from results of transform function being invoked on each element and its index in the original sequence.

fun <T, R> Sequence<T>.flatMapIndexed(
    transform: (index: Int, T) -> Iterable<R>
): Sequence<R>
fun <T, R> Sequence<T>.flatMapIndexed(
    transform: (index: Int, T) -> Sequence<R>
): Sequence<R>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

flatMapIndexedTo

Appends all elements yielded from results of transform function being invoked on each element and its index in the original sequence, to the given destination.

fun <T, R, C : MutableCollection<in R>> Sequence<T>.flatMapIndexedTo(
    destination: C, 
    transform: (index: Int, T) -> Iterable<R>
): C
fun <T, R, C : MutableCollection<in R>> Sequence<T>.flatMapIndexedTo(
    destination: C, 
    transform: (index: Int, T) -> Sequence<R>
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

flatMapTo

Appends all elements yielded from results of transform function being invoked on each element of original sequence, to the given destination.

fun <T, R, C : MutableCollection<in R>> Sequence<T>.flatMapTo(
    destination: C, 
    transform: (T) -> Iterable<R>
): C
fun <T, R, C : MutableCollection<in R>> Sequence<T>.flatMapTo(
    destination: C, 
    transform: (T) -> Sequence<R>
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

flatten

Returns a sequence of all elements from all sequences in this sequence.

fun <T> Sequence<Sequence<T>>.flatten(): Sequence<T>

Returns a sequence of all elements from all iterables in this sequence.

fun <T> Sequence<Iterable<T>>.flatten(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

fold

Accumulates value starting with initial value and applying operation from left to right to current accumulator value and each element.

fun <T, R> Sequence<T>.fold(
    initial: R, 
    operation: (acc: R, T) -> R
): R
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

foldIndexed

Accumulates value starting with initial value and applying operation from left to right to current accumulator value and each element with its index in the original sequence.

fun <T, R> Sequence<T>.foldIndexed(
    initial: R, 
    operation: (index: Int, acc: R, T) -> R
): R
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

forEach

Performs the given action on each element.

fun <T> Sequence<T>.forEach(action: (T) -> Unit)
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

forEachIndexed

Performs the given action on each element, providing sequential index with the element.

fun <T> Sequence<T>.forEachIndexed(
    action: (index: Int, T) -> Unit)
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

generateSequence

Returns a sequence which invokes the function to calculate the next value on each iteration until the function returns null.

fun <T : Any> generateSequence(
    nextFunction: () -> T?
): Sequence<T>

Returns a sequence defined by the starting value seed and the function nextFunction, which is invoked to calculate the next value based on the previous one on each iteration.

fun <T : Any> generateSequence(
    seed: T?, 
    nextFunction: (T) -> T?
): Sequence<T>

Returns a sequence defined by the function seedFunction, which is invoked to produce the starting value, and the nextFunction, which is invoked to calculate the next value based on the previous one on each iteration.

fun <T : Any> generateSequence(
    seedFunction: () -> T?, 
    nextFunction: (T) -> T?
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

groupBy

Groups elements of the original sequence by the key returned by the given keySelector function applied to each element and returns a map where each group key is associated with a list of corresponding elements.

fun <T, K> Sequence<T>.groupBy(
    keySelector: (T) -> K
): Map<K, List<T>>

Groups values returned by the valueTransform function applied to each element of the original sequence by the key returned by the given keySelector function applied to the element and returns a map where each group key is associated with a list of corresponding values.

fun <T, K, V> Sequence<T>.groupBy(
    keySelector: (T) -> K, 
    valueTransform: (T) -> V
): Map<K, List<V>>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

groupByTo

Groups elements of the original sequence by the key returned by the given keySelector function applied to each element and puts to the destination map each group key associated with a list of corresponding elements.

fun <T, K, M : MutableMap<in K, MutableList<T>>> Sequence<T>.groupByTo(
    destination: M, 
    keySelector: (T) -> K
): M

Groups values returned by the valueTransform function applied to each element of the original sequence by the key returned by the given keySelector function applied to the element and puts to the destination map each group key associated with a list of corresponding values.

fun <T, K, V, M : MutableMap<in K, MutableList<V>>> Sequence<T>.groupByTo(
    destination: M, 
    keySelector: (T) -> K, 
    valueTransform: (T) -> V
): M
Platform and version requirements: JVM (1.1), JS (1.1), Native (1.1)

groupingBy

Creates a Grouping source from a sequence to be used later with one of group-and-fold operations using the specified keySelector function to extract a key from each element.

fun <T, K> Sequence<T>.groupingBy(
    keySelector: (T) -> K
): Grouping<T, K>
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

ifEmpty

Returns a sequence that iterates through the elements either of this sequence or, if this sequence turns out to be empty, of the sequence returned by defaultValue function.

fun <T> Sequence<T>.ifEmpty(
    defaultValue: () -> Sequence<T>
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

indexOf

Returns first index of element, or -1 if the sequence does not contain element.

fun <T> Sequence<T>.indexOf(element: T): Int
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

indexOfFirst

Returns index of the first element matching the given predicate, or -1 if the sequence does not contain such element.

fun <T> Sequence<T>.indexOfFirst(
    predicate: (T) -> Boolean
): Int
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

indexOfLast

Returns index of the last element matching the given predicate, or -1 if the sequence does not contain such element.

fun <T> Sequence<T>.indexOfLast(
    predicate: (T) -> Boolean
): Int
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

iterator

Builds an Iterator lazily yielding values one by one.

fun <T> iterator(
    block: suspend SequenceScope<T>.() -> Unit
): Iterator<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

joinTo

Appends the string from all the elements separated using separator and using the given prefix and postfix if supplied.

fun <T, A : Appendable> Sequence<T>.joinTo(
    buffer: A, 
    separator: CharSequence = ", ", 
    prefix: CharSequence = "", 
    postfix: CharSequence = "", 
    limit: Int = -1, 
    truncated: CharSequence = "...", 
    transform: ((T) -> CharSequence)? = null
): A
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

joinToString

Creates a string from all the elements separated using separator and using the given prefix and postfix if supplied.

fun <T> Sequence<T>.joinToString(
    separator: CharSequence = ", ", 
    prefix: CharSequence = "", 
    postfix: CharSequence = "", 
    limit: Int = -1, 
    truncated: CharSequence = "...", 
    transform: ((T) -> CharSequence)? = null
): String
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

last

Returns the last element.

fun <T> Sequence<T>.last(): T

Returns the last element matching the given predicate.

fun <T> Sequence<T>.last(predicate: (T) -> Boolean): T
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

lastIndexOf

Returns last index of element, or -1 if the sequence does not contain element.

fun <T> Sequence<T>.lastIndexOf(element: T): Int
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

lastOrNull

Returns the last element, or null if the sequence is empty.

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

Returns the last element matching the given predicate, or null if no such element was found.

fun <T> Sequence<T>.lastOrNull(predicate: (T) -> Boolean): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

map

Returns a sequence containing the results of applying the given transform function to each element in the original sequence.

fun <T, R> Sequence<T>.map(transform: (T) -> R): Sequence<R>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

mapIndexed

Returns a sequence containing the results of applying the given transform function to each element and its index in the original sequence.

fun <T, R> Sequence<T>.mapIndexed(
    transform: (index: Int, T) -> R
): Sequence<R>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

mapIndexedNotNull

Returns a sequence containing only the non-null results of applying the given transform function to each element and its index in the original sequence.

fun <T, R : Any> Sequence<T>.mapIndexedNotNull(
    transform: (index: Int, T) -> R?
): Sequence<R>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

mapIndexedNotNullTo

Applies the given transform function to each element and its index in the original sequence and appends only the non-null results to the given destination.

fun <T, R : Any, C : MutableCollection<in R>> Sequence<T>.mapIndexedNotNullTo(
    destination: C, 
    transform: (index: Int, T) -> R?
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

mapIndexedTo

Applies the given transform function to each element and its index in the original sequence and appends the results to the given destination.

fun <T, R, C : MutableCollection<in R>> Sequence<T>.mapIndexedTo(
    destination: C, 
    transform: (index: Int, T) -> R
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

mapNotNull

Returns a sequence containing only the non-null results of applying the given transform function to each element in the original sequence.

fun <T, R : Any> Sequence<T>.mapNotNull(
    transform: (T) -> R?
): Sequence<R>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

mapNotNullTo

Applies the given transform function to each element in the original sequence and appends only the non-null results to the given destination.

fun <T, R : Any, C : MutableCollection<in R>> Sequence<T>.mapNotNullTo(
    destination: C, 
    transform: (T) -> R?
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

mapTo

Applies the given transform function to each element of the original sequence and appends the results to the given destination.

fun <T, R, C : MutableCollection<in R>> Sequence<T>.mapTo(
    destination: C, 
    transform: (T) -> R
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

max

fun Sequence<Double>.max(): Double?
fun Sequence<Float>.max(): Float?
fun <T : Comparable<T>> Sequence<T>.max(): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

maxBy

fun <T, R : Comparable<R>> Sequence<T>.maxBy(
    selector: (T) -> R
): T?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

maxByOrNull

Returns the first element yielding the largest value of the given function or null if there are no elements.

fun <T, R : Comparable<R>> Sequence<T>.maxByOrNull(
    selector: (T) -> R
): T?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

maxOf

Returns the largest value among all values produced by selector function applied to each element in the sequence.

fun <T> Sequence<T>.maxOf(selector: (T) -> Double): Double
fun <T> Sequence<T>.maxOf(selector: (T) -> Float): Float
fun <T, R : Comparable<R>> Sequence<T>.maxOf(
    selector: (T) -> R
): R
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

maxOfOrNull

Returns the largest value among all values produced by selector function applied to each element in the sequence or null if there are no elements.

fun <T> Sequence<T>.maxOfOrNull(
    selector: (T) -> Double
): Double?
fun <T> Sequence<T>.maxOfOrNull(
    selector: (T) -> Float
): Float?
fun <T, R : Comparable<R>> Sequence<T>.maxOfOrNull(
    selector: (T) -> R
): R?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

maxOfWith

Returns the largest value according to the provided comparator among all values produced by selector function applied to each element in the sequence.

fun <T, R> Sequence<T>.maxOfWith(
    comparator: Comparator<in R>, 
    selector: (T) -> R
): R
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

maxOfWithOrNull

Returns the largest value according to the provided comparator among all values produced by selector function applied to each element in the sequence or null if there are no elements.

fun <T, R> Sequence<T>.maxOfWithOrNull(
    comparator: Comparator<in R>, 
    selector: (T) -> R
): R?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

maxOrNull

Returns the largest element or null if there are no elements.

fun Sequence<Double>.maxOrNull(): Double?
fun Sequence<Float>.maxOrNull(): Float?
fun <T : Comparable<T>> Sequence<T>.maxOrNull(): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

maxWith

fun <T> Sequence<T>.maxWith(comparator: Comparator<in T>): T?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

maxWithOrNull

Returns the first element having the largest value according to the provided comparator or null if there are no elements.

fun <T> Sequence<T>.maxWithOrNull(
    comparator: Comparator<in T>
): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

min

fun Sequence<Double>.min(): Double?
fun Sequence<Float>.min(): Float?
fun <T : Comparable<T>> Sequence<T>.min(): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

minBy

fun <T, R : Comparable<R>> Sequence<T>.minBy(
    selector: (T) -> R
): T?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

minByOrNull

Returns the first element yielding the smallest value of the given function or null if there are no elements.

fun <T, R : Comparable<R>> Sequence<T>.minByOrNull(
    selector: (T) -> R
): T?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

minOf

Returns the smallest value among all values produced by selector function applied to each element in the sequence.

fun <T> Sequence<T>.minOf(selector: (T) -> Double): Double
fun <T> Sequence<T>.minOf(selector: (T) -> Float): Float
fun <T, R : Comparable<R>> Sequence<T>.minOf(
    selector: (T) -> R
): R
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

minOfOrNull

Returns the smallest value among all values produced by selector function applied to each element in the sequence or null if there are no elements.

fun <T> Sequence<T>.minOfOrNull(
    selector: (T) -> Double
): Double?
fun <T> Sequence<T>.minOfOrNull(
    selector: (T) -> Float
): Float?
fun <T, R : Comparable<R>> Sequence<T>.minOfOrNull(
    selector: (T) -> R
): R?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

minOfWith

Returns the smallest value according to the provided comparator among all values produced by selector function applied to each element in the sequence.

fun <T, R> Sequence<T>.minOfWith(
    comparator: Comparator<in R>, 
    selector: (T) -> R
): R
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

minOfWithOrNull

Returns the smallest value according to the provided comparator among all values produced by selector function applied to each element in the sequence or null if there are no elements.

fun <T, R> Sequence<T>.minOfWithOrNull(
    comparator: Comparator<in R>, 
    selector: (T) -> R
): R?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

minOrNull

Returns the smallest element or null if there are no elements.

fun Sequence<Double>.minOrNull(): Double?
fun Sequence<Float>.minOrNull(): Float?
fun <T : Comparable<T>> Sequence<T>.minOrNull(): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

minus

Returns a sequence containing all elements of the original sequence without the first occurrence of the given element.

operator fun <T> Sequence<T>.minus(element: T): Sequence<T>

Returns a sequence containing all elements of original sequence except the elements contained in the given elements array.

operator fun <T> Sequence<T>.minus(
    elements: Array<out T>
): Sequence<T>

Returns a sequence containing all elements of original sequence except the elements contained in the given elements collection.

operator fun <T> Sequence<T>.minus(
    elements: Iterable<T>
): Sequence<T>

Returns a sequence containing all elements of original sequence except the elements contained in the given elements sequence.

operator fun <T> Sequence<T>.minus(
    elements: Sequence<T>
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

minusElement

Returns a sequence containing all elements of the original sequence without the first occurrence of the given element.

fun <T> Sequence<T>.minusElement(element: T): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

minWith

fun <T> Sequence<T>.minWith(comparator: Comparator<in T>): T?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

minWithOrNull

Returns the first element having the smallest value according to the provided comparator or null if there are no elements.

fun <T> Sequence<T>.minWithOrNull(
    comparator: Comparator<in T>
): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

none

Returns true if the sequence has no elements.

fun <T> Sequence<T>.none(): Boolean

Returns true if no elements match the given predicate.

fun <T> Sequence<T>.none(predicate: (T) -> Boolean): Boolean
Platform and version requirements: JVM (1.1), JS (1.1), Native (1.1)

onEach

Returns a sequence which performs the given action on each element of the original sequence as they pass through it.

fun <T> Sequence<T>.onEach(action: (T) -> Unit): Sequence<T>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

onEachIndexed

Returns a sequence which performs the given action on each element of the original sequence as they pass through it.

fun <T> Sequence<T>.onEachIndexed(
    action: (index: Int, T) -> Unit
): Sequence<T>
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

orEmpty

Returns this sequence if it's not null and the empty sequence otherwise.

fun <T> Sequence<T>?.orEmpty(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

partition

Splits the original sequence into pair of lists, where first list contains elements for which predicate yielded true, while second list contains elements for which predicate yielded false.

fun <T> Sequence<T>.partition(
    predicate: (T) -> Boolean
): Pair<List<T>, List<T>>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

plus

Returns a sequence containing all elements of the original sequence and then the given element.

operator fun <T> Sequence<T>.plus(element: T): Sequence<T>

Returns a sequence containing all elements of original sequence and then all elements of the given elements array.

operator fun <T> Sequence<T>.plus(
    elements: Array<out T>
): Sequence<T>

Returns a sequence containing all elements of original sequence and then all elements of the given elements collection.

operator fun <T> Sequence<T>.plus(
    elements: Iterable<T>
): Sequence<T>

Returns a sequence containing all elements of original sequence and then all elements of the given elements sequence.

operator fun <T> Sequence<T>.plus(
    elements: Sequence<T>
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

plusElement

Returns a sequence containing all elements of the original sequence and then the given element.

fun <T> Sequence<T>.plusElement(element: T): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

reduce

Accumulates value starting with the first element and applying operation from left to right to current accumulator value and each element.

fun <S, T : S> Sequence<T>.reduce(
    operation: (acc: S, T) -> S
): S
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

reduceIndexed

Accumulates value starting with the first element and applying operation from left to right to current accumulator value and each element with its index in the original sequence.

fun <S, T : S> Sequence<T>.reduceIndexed(
    operation: (index: Int, acc: S, T) -> S
): S
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

reduceIndexedOrNull

Accumulates value starting with the first element and applying operation from left to right to current accumulator value and each element with its index in the original sequence.

fun <S, T : S> Sequence<T>.reduceIndexedOrNull(
    operation: (index: Int, acc: S, T) -> S
): S?
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

reduceOrNull

Accumulates value starting with the first element and applying operation from left to right to current accumulator value and each element.

fun <S, T : S> Sequence<T>.reduceOrNull(
    operation: (acc: S, T) -> S
): S?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

requireNoNulls

Returns an original collection containing all the non-null elements, throwing an IllegalArgumentException if there are any null elements.

fun <T : Any> Sequence<T?>.requireNoNulls(): Sequence<T>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

runningFold

Returns a sequence containing successive accumulation values generated by applying operation from left to right to each element and current accumulator value that starts with initial value.

fun <T, R> Sequence<T>.runningFold(
    initial: R, 
    operation: (acc: R, T) -> R
): Sequence<R>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

runningFoldIndexed

Returns a sequence containing successive accumulation values generated by applying operation from left to right to each element, its index in the original sequence and current accumulator value that starts with initial value.

fun <T, R> Sequence<T>.runningFoldIndexed(
    initial: R, 
    operation: (index: Int, acc: R, T) -> R
): Sequence<R>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

runningReduce

Returns a sequence containing successive accumulation values generated by applying operation from left to right to each element and current accumulator value that starts with the first element of this sequence.

fun <S, T : S> Sequence<T>.runningReduce(
    operation: (acc: S, T) -> S
): Sequence<S>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

runningReduceIndexed

Returns a sequence containing successive accumulation values generated by applying operation from left to right to each element, its index in the original sequence and current accumulator value that starts with the first element of this sequence.

fun <S, T : S> Sequence<T>.runningReduceIndexed(
    operation: (index: Int, acc: S, T) -> S
): Sequence<S>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

scan

Returns a sequence containing successive accumulation values generated by applying operation from left to right to each element and current accumulator value that starts with initial value.

fun <T, R> Sequence<T>.scan(
    initial: R, 
    operation: (acc: R, T) -> R
): Sequence<R>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

scanIndexed

Returns a sequence containing successive accumulation values generated by applying operation from left to right to each element, its index in the original sequence and current accumulator value that starts with initial value.

fun <T, R> Sequence<T>.scanIndexed(
    initial: R, 
    operation: (index: Int, acc: R, T) -> R
): Sequence<R>
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

scanReduce

fun <S, T : S> Sequence<T>.scanReduce(
    operation: (acc: S, T) -> S
): Sequence<S>
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

scanReduceIndexed

fun <S, T : S> Sequence<T>.scanReduceIndexed(
    operation: (index: Int, acc: S, T) -> S
): Sequence<S>
Platform and version requirements: JVM (1.3), JS (1.3), Native (1.3)

sequence

Builds a Sequence lazily yielding values one by one.

fun <T> sequence(
    block: suspend SequenceScope<T>.() -> Unit
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

Sequence

Given an iterator function constructs a Sequence that returns values through the Iterator provided by that function. The values are evaluated lazily, and the sequence is potentially infinite.

fun <T> Sequence(iterator: () -> Iterator<T>): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sequenceOf

Creates a sequence that returns the specified values.

fun <T> sequenceOf(vararg elements: T): Sequence<T>
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

shuffled

Returns a sequence that yields elements of this sequence randomly shuffled.

fun <T> Sequence<T>.shuffled(): Sequence<T>

Returns a sequence that yields elements of this sequence randomly shuffled using the specified random instance as the source of randomness.

fun <T> Sequence<T>.shuffled(random: Random): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

single

Returns the single element, or throws an exception if the sequence is empty or has more than one element.

fun <T> Sequence<T>.single(): T

Returns the single element matching the given predicate, or throws exception if there is no or more than one matching element.

fun <T> Sequence<T>.single(predicate: (T) -> Boolean): T
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

singleOrNull

Returns single element, or null if the sequence is empty or has more than one element.

fun <T> Sequence<T>.singleOrNull(): T?

Returns the single element matching the given predicate, or null if element was not found or more than one element was found.

fun <T> Sequence<T>.singleOrNull(
    predicate: (T) -> Boolean
): T?
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sorted

Returns a sequence that yields elements of this sequence sorted according to their natural sort order.

fun <T : Comparable<T>> Sequence<T>.sorted(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sortedBy

Returns a sequence that yields elements of this sequence sorted according to natural sort order of the value returned by specified selector function.

fun <T, R : Comparable<R>> Sequence<T>.sortedBy(
    selector: (T) -> R?
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sortedByDescending

Returns a sequence that yields elements of this sequence sorted descending according to natural sort order of the value returned by specified selector function.

fun <T, R : Comparable<R>> Sequence<T>.sortedByDescending(
    selector: (T) -> R?
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sortedDescending

Returns a sequence that yields elements of this sequence sorted descending according to their natural sort order.

fun <T : Comparable<T>> Sequence<T>.sortedDescending(): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sortedWith

Returns a sequence that yields elements of this sequence sorted according to the specified comparator.

fun <T> Sequence<T>.sortedWith(
    comparator: Comparator<in T>
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sum

Returns the sum of all elements in the sequence.

fun Sequence<Byte>.sum(): Int
fun Sequence<Short>.sum(): Int
fun Sequence<Int>.sum(): Int
fun Sequence<Long>.sum(): Long
fun Sequence<Float>.sum(): Float
fun Sequence<Double>.sum(): Double
fun Sequence<UInt>.sum(): UInt
fun Sequence<ULong>.sum(): ULong
fun Sequence<UByte>.sum(): UInt
fun Sequence<UShort>.sum(): UInt
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sumBy

Returns the sum of all values produced by selector function applied to each element in the sequence.

fun <T> Sequence<T>.sumBy(selector: (T) -> Int): Int
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

sumByDouble

Returns the sum of all values produced by selector function applied to each element in the sequence.

fun <T> Sequence<T>.sumByDouble(
    selector: (T) -> Double
): Double

sumOf

Returns the sum of all values produced by selector function applied to each element in the sequence.

Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)
fun <T> Sequence<T>.sumOf(selector: (T) -> Double): Double
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)
fun <T> Sequence<T>.sumOf(selector: (T) -> Int): Int
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)
fun <T> Sequence<T>.sumOf(selector: (T) -> Long): Long
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)
fun <T> Sequence<T>.sumOf(selector: (T) -> UInt): UInt
Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)
fun <T> Sequence<T>.sumOf(selector: (T) -> ULong): ULong
Platform and version requirements: JVM (1.4)
fun <T> Sequence<T>.sumOf(
    selector: (T) -> BigDecimal
): BigDecimal
Platform and version requirements: JVM (1.4)
fun <T> Sequence<T>.sumOf(
    selector: (T) -> BigInteger
): BigInteger
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

take

Returns a sequence containing first n elements.

fun <T> Sequence<T>.take(n: Int): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

takeWhile

Returns a sequence containing first elements satisfying the given predicate.

fun <T> Sequence<T>.takeWhile(
    predicate: (T) -> Boolean
): Sequence<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

toCollection

Appends all elements to the given destination collection.

fun <T, C : MutableCollection<in T>> Sequence<T>.toCollection(
    destination: C
): C
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

toHashSet

Returns a new HashSet of all elements.

fun <T> Sequence<T>.toHashSet(): HashSet<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

toList

Returns a List containing all elements.

fun <T> Sequence<T>.toList(): List<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

toMutableList

Returns a new MutableList filled with all elements of this sequence.

fun <T> Sequence<T>.toMutableList(): MutableList<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

toMutableSet

Returns a new MutableSet containing all distinct elements from the given sequence.

fun <T> Sequence<T>.toMutableSet(): MutableSet<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

toSet

Returns a Set of all elements.

fun <T> Sequence<T>.toSet(): Set<T>
Platform and version requirements: JVM (1.0)

toSortedSet

Returns a new SortedSet of all elements.

fun <T : Comparable<T>> Sequence<T>.toSortedSet(): SortedSet<T>
fun <T> Sequence<T>.toSortedSet(
    comparator: Comparator<in T>
): SortedSet<T>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

unzip

Returns a pair of lists, where first list is built from the first values of each pair from this sequence, second list is built from the second values of each pair from this sequence.

fun <T, R> Sequence<Pair<T, R>>.unzip(): Pair<List<T>, List<R>>
Platform and version requirements: JVM (1.2), JS (1.2), Native (1.2)

windowed

Returns a sequence of snapshots of the window of the given size sliding along this sequence with the given step, where each snapshot is a list.

fun <T> Sequence<T>.windowed(
    size: Int, 
    step: Int = 1, 
    partialWindows: Boolean = false
): Sequence<List<T>>

Returns a sequence of results of applying the given transform function to an each list representing a view over the window of the given size sliding along this sequence with the given step.

fun <T, R> Sequence<T>.windowed(
    size: Int, 
    step: Int = 1, 
    partialWindows: Boolean = false, 
    transform: (List<T>) -> R
): Sequence<R>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

withIndex

Returns a sequence that wraps each element of the original sequence into an IndexedValue containing the index of that element and the element itself.

fun <T> Sequence<T>.withIndex(): Sequence<IndexedValue<T>>
Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

zip

Returns a sequence of values built from the elements of this sequence and the other sequence with the same index. The resulting sequence ends as soon as the shortest input sequence ends.

infix fun <T, R> Sequence<T>.zip(
    other: Sequence<R>
): Sequence<Pair<T, R>>

Returns a sequence of values built from the elements of this sequence and the other sequence with the same index using the provided transform function applied to each pair of elements. The resulting sequence ends as soon as the shortest input sequence ends.

fun <T, R, V> Sequence<T>.zip(
    other: Sequence<R>, 
    transform: (a: T, b: R) -> V
): Sequence<V>
Platform and version requirements: JVM (1.2), JS (1.2), Native (1.2)

zipWithNext

Returns a sequence of pairs of each two adjacent elements in this sequence.

fun <T> Sequence<T>.zipWithNext(): Sequence<Pair<T, T>>

Returns a sequence containing the results of applying the given transform function to an each pair of two adjacent elements in this sequence.

fun <T, R> Sequence<T>.zipWithNext(
    transform: (a: T, b: T) -> R
): Sequence<R>

© 2010–2020 JetBrains s.r.o. and Kotlin Programming Language contributors
Licensed under the Apache License, Version 2.0.
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.sequences/index.html