kotlin-stdlib / kotlin.sequences / Sequence

Sequence

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interface Sequence<out T>
(source)

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

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. generateSequence overload). The latter sequences throw an exception on an attempt to iterate them the second time.

Sequence operations, like Sequence.map, Sequence.filter etc, generally preserve that property of a sequence, and again it's documented for an operation if it doesn't.

Parameters

T - the type of elements in the sequence.

Functions

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iterator

Returns an Iterator that returns the values from the sequence.

abstract operator fun iterator(): Iterator<T>

Extension Functions

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all

Returns true if all elements match the given predicate.

fun <T> Sequence<T>.all(predicate: (T) -> Boolean): Boolean
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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
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asIterable

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

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

Returns this sequence as a Sequence.

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

Returns true if element is found in the sequence.

operator fun <T> Sequence<T>.contains(element: T): Boolean
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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
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distinct

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

fun <T> Sequence<T>.distinct(): Sequence<T>
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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>
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drop

Returns a sequence containing all elements except first n elements.

fun <T> Sequence<T>.drop(n: Int): Sequence<T>
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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>
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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
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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
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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?
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filter

Returns a sequence containing only elements matching the given predicate.

fun <T> Sequence<T>.filter(
    predicate: (T) -> Boolean
): Sequence<T>
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filterIndexed

Returns a sequence containing only elements matching the given predicate.

fun <T> Sequence<T>.filterIndexed(
    predicate: (index: Int, T) -> Boolean
): Sequence<T>
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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

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

fun <R> Sequence<*>.filterIsInstance(): Sequence<R>
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Returns a sequence containing all elements that are instances of specified class.

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

filterIsInstanceTo

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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
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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
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filterNot

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

fun <T> Sequence<T>.filterNot(
    predicate: (T) -> Boolean
): Sequence<T>
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filterNotNull

Returns a sequence containing all elements that are not null.

fun <T : Any> Sequence<T?>.filterNotNull(): Sequence<T>
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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
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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
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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
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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?
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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?
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first

Returns the 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
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firstNotNullOf

Returns the first non-null value produced by transform function being applied to elements of this sequence in iteration order, or throws NoSuchElementException if no non-null value was produced.

fun <T, R : Any> Sequence<T>.firstNotNullOf(
    transform: (T) -> R?
): R
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firstNotNullOfOrNull

Returns the first non-null value produced by transform function being applied to elements of this sequence in iteration order, or null if no non-null value was produced.

fun <T, R : Any> Sequence<T>.firstNotNullOfOrNull(
    transform: (T) -> R?
): R?
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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?
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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>
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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>
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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
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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
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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>
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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
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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
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forEach

Performs the given action on each element.

fun <T> Sequence<T>.forEach(action: (T) -> Unit)
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forEachIndexed

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

fun <T> Sequence<T>.forEachIndexed(
    action: (index: Int, T) -> Unit)
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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>>
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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
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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>
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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>
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indexOf

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

fun <T> Sequence<T>.indexOf(element: T): Int
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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
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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
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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
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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
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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
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lastIndexOf

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

fun <T> Sequence<T>.lastIndexOf(element: T): Int
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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?
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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>
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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>
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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>
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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
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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
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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>
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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
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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
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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?
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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
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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?
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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
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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?
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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?

maxWith

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Returns the first element having the largest value according to the provided comparator.

fun <T> Sequence<T>.maxWith(comparator: Comparator<in T>): T
JVM
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fun <T> Sequence<T>.maxWith(comparator: Comparator<in T>): T?
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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?
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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?
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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
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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?
Common
JVM
JS
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
Common
JVM
JS
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?
Common
JVM
JS
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?
Common
JVM
JS
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>
Common
JVM
JS
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>

minWith

Common
JVM
JS
Native
1.7

Returns the first element having the smallest value according to the provided comparator.

fun <T> Sequence<T>.minWith(comparator: Comparator<in T>): T
JVM
1.0
fun <T> Sequence<T>.minWith(comparator: Comparator<in T>): T?
Common
JVM
JS
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?
Common
JVM
JS
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
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
Native
1.3

orEmpty

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

fun <T> Sequence<T>?.orEmpty(): Sequence<T>
Common
JVM
JS
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>>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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
Common
JVM
JS
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
Common
JVM
JS
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?
Common
JVM
JS
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?
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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
Common
JVM
JS
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?
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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>
Common
JVM
JS
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
Common
JVM
JS
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
Common
JVM
JS
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.

Common
JVM
JS
Native
1.4
fun <T> Sequence<T>.sumOf(selector: (T) -> Double): Double
Common
JVM
JS
Native
1.4
fun <T> Sequence<T>.sumOf(selector: (T) -> Int): Int
Common
JVM
JS
Native
1.4
fun <T> Sequence<T>.sumOf(selector: (T) -> Long): Long
Common
JVM
JS
Native
1.5
fun <T> Sequence<T>.sumOf(selector: (T) -> UInt): UInt
Common
JVM
JS
Native
1.5
fun <T> Sequence<T>.sumOf(selector: (T) -> ULong): ULong
JVM
1.4
fun <T> Sequence<T>.sumOf(
    selector: (T) -> BigDecimal
): BigDecimal
JVM
1.4
fun <T> Sequence<T>.sumOf(
    selector: (T) -> BigInteger
): BigInteger
Common
JVM
JS
Native
1.0

take

Returns a sequence containing first n elements.

fun <T> Sequence<T>.take(n: Int): Sequence<T>
Common
JVM
JS
Native
1.0

takeWhile

Returns a sequence containing first elements satisfying the given predicate.

fun <T> Sequence<T>.takeWhile(
    predicate: (T) -> Boolean
): Sequence<T>
Common
JVM
JS
Native
1.0

toCollection

Appends all elements to the given destination collection.

fun <T, C : MutableCollection<in T>> Sequence<T>.toCollection(
    destination: C
): C
Common
JVM
JS
Native
1.0

toHashSet

Returns a new HashSet of all elements.

fun <T> Sequence<T>.toHashSet(): HashSet<T>
Common
JVM
JS
Native
1.0

toList

Returns a List containing all elements.

fun <T> Sequence<T>.toList(): List<T>
Common
JVM
JS
Native
1.0

toMap

Returns a new map containing all key-value pairs from the given sequence of pairs.

fun <K, V> Sequence<Pair<K, V>>.toMap(): Map<K, V>

Populates and returns the destination mutable map with key-value pairs from the given sequence of pairs.

fun <K, V, M : MutableMap<in K, in V>> Sequence<Pair<K, V>>.toMap(
    destination: M
): M
Common
JVM
JS
Native
1.0

toMutableList

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

fun <T> Sequence<T>.toMutableList(): MutableList<T>
Common
JVM
JS
Native
1.0

toMutableSet

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

fun <T> Sequence<T>.toMutableSet(): MutableSet<T>
Common
JVM
JS
Native
1.0

toSet

Returns a Set of all elements.

fun <T> Sequence<T>.toSet(): Set<T>
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>
Common
JVM
JS
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>>
Common
JVM
JS
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>
Common
JVM
JS
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>>
Common
JVM
JS
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>
Common
JVM
JS
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>

Inheritors

JVM
1.0

FileTreeWalk

This class is intended to implement different file traversal methods. It allows to iterate through all files inside a given directory.

class FileTreeWalk : Sequence<File>