kotlin-stdlib/kotlin.sequences

Package-level declarations

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:

stateless – operations which require no state and process each element independently like kotlin.sequences.Sequence.map, kotlin.sequences.Sequence.filter, or require a small constant amount of state to process an element, for example kotlin.sequences.Sequence.take or kotlin.sequences.Sequence.drop;
stateful – operations which require a significant amount of state, usually proportional to the number of elements in a sequence.

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.

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:

stateless – operations which require no state and process each element independently like kotlin.sequences.Sequence.map, kotlin.sequences.Sequence.filter, or require a small constant amount of state to process an element, for example kotlin.sequences.Sequence.take or kotlin.sequences.Sequence.drop;
stateful – operations which require a significant amount of state, usually proportional to the number of elements in a sequence.

Types

Sequence

interface Sequence<out T>

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

Since Kotlin 1.0

SequenceBuilder

typealias ~~SequenceBuilder<T>~~ = SequenceScope<T>

Since Kotlin 1.0

SequenceScope

abstract class SequenceScope<in T>

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

Since Kotlin 1.3

Functions

all

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

Returns true if all elements match the given predicate.

Since Kotlin 1.0

any

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

Returns true if sequence has at least one element.

Since Kotlin 1.0

inline fun <T> Sequence<T>.any(predicate: (T) -> Boolean): Boolean

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

Since Kotlin 1.0

asIterable

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

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

Since Kotlin 1.0

asSequence

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

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

Since Kotlin 1.0

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

Returns this sequence as a Sequence.

Since Kotlin 1.0

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

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

Since Kotlin 1.0

associate

inline fun <T, K, V> Sequence<T>.associate(transform: (T) -> Pair<K, V>): Map<K, V>

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

Since Kotlin 1.0

associateBy

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

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

Since Kotlin 1.0

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

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

Since Kotlin 1.0

associateByTo

inline 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 applied to each element of the given sequence and value is the element itself.

Since Kotlin 1.0

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

Since Kotlin 1.0

associateTo

inline fun <T, K, V, M : MutableMap<in K, in V>> Sequence<T>.associateTo(destination: M, transform: (T) -> Pair<K, V>): M

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

Since Kotlin 1.0

associateWith

inline fun <K, V> Sequence<K>.associateWith(valueSelector: (K) -> V): Map<K, V>

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

Since Kotlin 1.3

associateWithTo

inline fun <K, V, M : MutableMap<in K, in V>> Sequence<K>.associateWithTo(destination: M, valueSelector: (K) -> V): M

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.

Since Kotlin 1.3

average

@JvmName(name = "averageOfByte")

fun Sequence<Byte>.average(): Double

@JvmName(name = "averageOfDouble")

fun Sequence<Double>.average(): Double

@JvmName(name = "averageOfFloat")

fun Sequence<Float>.average(): Double

@JvmName(name = "averageOfInt")

fun Sequence<Int>.average(): Double

@JvmName(name = "averageOfLong")

fun Sequence<Long>.average(): Double

@JvmName(name = "averageOfShort")

fun Sequence<Short>.average(): Double

Returns an average value of elements in the sequence.

Since Kotlin 1.0

buildIterator

inline fun <T> ~~buildIterator~~(noinline builderAction: suspend SequenceScope<T>.() -> Unit): Iterator<T>

Since Kotlin 1.3

buildSequence

inline fun <T> ~~buildSequence~~(noinline builderAction: suspend SequenceScope<T>.() -> Unit): Sequence<T>

Since Kotlin 1.3

chunked

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

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

Since Kotlin 1.2

fun <T, R> Sequence<T>.chunked(size: Int, transform: (List<T>) -> R): Sequence<R>

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

Since Kotlin 1.2

constrainOnce

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

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

Since Kotlin 1.0

contains

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

Returns true if element is found in the sequence.

Since Kotlin 1.0

count

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

Returns the number of elements in this sequence.

Since Kotlin 1.0

inline fun <T> Sequence<T>.count(predicate: (T) -> Boolean): Int

Returns the number of elements matching the given predicate.

Since Kotlin 1.0

distinct

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

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

Since Kotlin 1.0

distinctBy

fun <T, K> Sequence<T>.distinctBy(selector: (T) -> K): Sequence<T>

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

Since Kotlin 1.0

drop

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

Returns a sequence containing all elements except first n elements.

Since Kotlin 1.0

dropWhile

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

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

Since Kotlin 1.0

elementAt

fun <T> Sequence<T>.elementAt(index: Int): T

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

Since Kotlin 1.0

elementAtOrElse

fun <T> Sequence<T>.elementAtOrElse(index: Int, defaultValue: (Int) -> T): T

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.

Since Kotlin 1.0

elementAtOrNull

fun <T> Sequence<T>.elementAtOrNull(index: Int): T?

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

Since Kotlin 1.0

emptySequence

fun <T> emptySequence(): Sequence<T>

Returns an empty sequence.

Since Kotlin 1.0

filter

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

Returns a sequence containing only elements matching the given predicate.

Since Kotlin 1.0

filterIndexed

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

Returns a sequence containing only elements matching the given predicate.

Since Kotlin 1.0

filterIndexedTo

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

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

Since Kotlin 1.0

filterIsInstance

inline fun <R> Sequence<*>.filterIsInstance(): Sequence<R>

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

Since Kotlin 1.0

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

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

Since Kotlin 1.0

filterIsInstanceTo

inline fun <R, C : MutableCollection<in R>> Sequence<*>.filterIsInstanceTo(destination: C): C

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

Since Kotlin 1.0

fun <C : MutableCollection<in R>, R> Sequence<*>.filterIsInstanceTo(destination: C, klass: Class<R>): C

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

Since Kotlin 1.0

filterNot

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

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

Since Kotlin 1.0

filterNotNull

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

Returns a sequence containing all elements that are not null.

Since Kotlin 1.0

filterNotNullTo

fun <C : MutableCollection<in T>, T : Any> Sequence<T?>.filterNotNullTo(destination: C): C

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

Since Kotlin 1.0

filterNotTo

inline fun <T, C : MutableCollection<in T>> Sequence<T>.filterNotTo(destination: C, predicate: (T) -> Boolean): C

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

Since Kotlin 1.0

filterTo

inline fun <T, C : MutableCollection<in T>> Sequence<T>.filterTo(destination: C, predicate: (T) -> Boolean): C

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

Since Kotlin 1.0

find

inline fun <T> Sequence<T>.find(predicate: (T) -> Boolean): T?

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

Since Kotlin 1.0

findLast

inline fun <T> Sequence<T>.findLast(predicate: (T) -> Boolean): T?

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

Since Kotlin 1.0

first

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

Returns first element.

Since Kotlin 1.0

inline fun <T> Sequence<T>.first(predicate: (T) -> Boolean): T

Returns the first element matching the given predicate.

Since Kotlin 1.0

firstNotNullOf

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

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.

Since Kotlin 1.5

firstNotNullOfOrNull

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

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.

Since Kotlin 1.5

firstOrNull

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

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

Since Kotlin 1.0

inline fun <T> Sequence<T>.firstOrNull(predicate: (T) -> Boolean): T?

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

Since Kotlin 1.0

flatMap

@JvmName(name = "flatMapIterable")

fun <T, R> Sequence<T>.flatMap(transform: (T) -> Iterable<R>): Sequence<R>

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

Since Kotlin 1.4

fun <T, R> Sequence<T>.flatMap(transform: (T) -> Sequence<R>): Sequence<R>

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

Since Kotlin 1.0

flatMapIndexed

@JvmName(name = "flatMapIndexedIterable")

fun <T, R> Sequence<T>.flatMapIndexed(transform: (index: Int, T) -> Iterable<R>): Sequence<R>

@JvmName(name = "flatMapIndexedSequence")

fun <T, R> Sequence<T>.flatMapIndexed(transform: (index: Int, T) -> Sequence<R>): Sequence<R>

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.

Since Kotlin 1.4

flatMapIndexedTo

@JvmName(name = "flatMapIndexedIterableTo")

inline fun <T, R, C : MutableCollection<in R>> Sequence<T>.flatMapIndexedTo(destination: C, transform: (index: Int, T) -> Iterable<R>): C

@JvmName(name = "flatMapIndexedSequenceTo")

inline fun <T, R, C : MutableCollection<in R>> Sequence<T>.flatMapIndexedTo(destination: C, transform: (index: Int, T) -> Sequence<R>): C

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.

Since Kotlin 1.4

flatMapTo

@JvmName(name = "flatMapIterableTo")

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

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

Since Kotlin 1.4

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

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

Since Kotlin 1.0

flatten

@JvmName(name = "flattenSequenceOfIterable")

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

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

Since Kotlin 1.0

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

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

Since Kotlin 1.0

fold

inline fun <T, R> Sequence<T>.fold(initial: R, operation: (acc: R, T) -> R): R

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

Since Kotlin 1.0

foldIndexed

inline fun <T, R> Sequence<T>.foldIndexed(initial: R, operation: (index: Int, acc: R, T) -> R): R

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.

Since Kotlin 1.0

forEach

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

Performs the given action on each element.

Since Kotlin 1.0

forEachIndexed

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

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

Since Kotlin 1.0

generateSequence

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

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

Since Kotlin 1.0

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

Since Kotlin 1.0

fun <T : Any> generateSequence(seedFunction: () -> 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.

Since Kotlin 1.0

groupBy

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

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.

Since Kotlin 1.0

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

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.

Since Kotlin 1.0

groupByTo

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

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.

Since Kotlin 1.0

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

Since Kotlin 1.0

groupingBy

inline fun <T, K> Sequence<T>.groupingBy(crossinline keySelector: (T) -> K): Grouping<T, K>

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.

Since Kotlin 1.1

ifEmpty

fun <T> Sequence<T>.ifEmpty(defaultValue: () -> Sequence<T>): Sequence<T>

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.

Since Kotlin 1.3

indexOf

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

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

Since Kotlin 1.0

indexOfFirst

inline fun <T> Sequence<T>.indexOfFirst(predicate: (T) -> Boolean): Int

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

Since Kotlin 1.0

indexOfLast

inline fun <T> Sequence<T>.indexOfLast(predicate: (T) -> Boolean): Int

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

Since Kotlin 1.0

iterator

fun <T> iterator(block: suspend SequenceScope<T>.() -> Unit): Iterator<T>

Builds an Iterator lazily yielding values one by one.

Since Kotlin 1.3

joinTo

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

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

Since Kotlin 1.0

joinToString

fun <T> Sequence<T>.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (T) -> CharSequence? = null): String

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

Since Kotlin 1.0

last

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

Returns the last element.

Since Kotlin 1.0

inline fun <T> Sequence<T>.last(predicate: (T) -> Boolean): T

Returns the last element matching the given predicate.

Since Kotlin 1.0

lastIndexOf

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

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

Since Kotlin 1.0

lastOrNull

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

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

Since Kotlin 1.0

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

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

Since Kotlin 1.0

map

fun <T, R> Sequence<T>.map(transform: (T) -> R): Sequence<R>

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

Since Kotlin 1.0

mapIndexed

fun <T, R> Sequence<T>.mapIndexed(transform: (index: Int, T) -> R): Sequence<R>

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

Since Kotlin 1.0

mapIndexedNotNull

fun <T, R : Any> Sequence<T>.mapIndexedNotNull(transform: (index: Int, T) -> R?): Sequence<R>

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.

Since Kotlin 1.0

mapIndexedNotNullTo

inline fun <T, R : Any, C : MutableCollection<in R>> Sequence<T>.mapIndexedNotNullTo(destination: C, transform: (index: Int, T) -> R?): C

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.

Since Kotlin 1.0

mapIndexedTo

inline fun <T, R, C : MutableCollection<in R>> Sequence<T>.mapIndexedTo(destination: C, transform: (index: Int, T) -> R): C

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

Since Kotlin 1.0

mapNotNull

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

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

Since Kotlin 1.0

mapNotNullTo

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

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

Since Kotlin 1.0

mapTo

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

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

Since Kotlin 1.0

max

fun <T : Comparable<T>> Sequence<T>.~~max~~(): T?

Since Kotlin 1.0

fun Sequence<Double>.~~max~~(): Double?

fun Sequence<Float>.~~max~~(): Float?

Since Kotlin 1.1

maxBy

inline fun <T, R : Comparable<R>> Sequence<T>.~~maxBy~~(selector: (T) -> R): T?

Since Kotlin 1.0

maxByOrNull

inline fun <T, R : Comparable<R>> Sequence<T>.maxByOrNull(selector: (T) -> R): T?

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

Since Kotlin 1.4

maxOf

inline fun <T, R : Comparable<R>> Sequence<T>.maxOf(selector: (T) -> R): R

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

inline fun <T> Sequence<T>.maxOf(selector: (T) -> Float): Float

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

Since Kotlin 1.4

maxOfOrNull

inline fun <T, R : Comparable<R>> Sequence<T>.maxOfOrNull(selector: (T) -> R): R?

inline fun <T> Sequence<T>.maxOfOrNull(selector: (T) -> Double): Double?

inline fun <T> Sequence<T>.maxOfOrNull(selector: (T) -> Float): Float?

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.

Since Kotlin 1.4

maxOfWith

inline fun <T, R> Sequence<T>.maxOfWith(comparator: Comparator<in R>, selector: (T) -> R): R

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

Since Kotlin 1.4

maxOfWithOrNull

inline fun <T, R> Sequence<T>.maxOfWithOrNull(comparator: Comparator<in R>, selector: (T) -> R): R?

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.

Since Kotlin 1.4

maxOrNull

fun <T : Comparable<T>> Sequence<T>.maxOrNull(): T?

fun Sequence<Double>.maxOrNull(): Double?

fun Sequence<Float>.maxOrNull(): Float?

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

Since Kotlin 1.4

maxWith

fun <T> Sequence<T>.~~maxWith~~(comparator: Comparator<in T>): T?

Since Kotlin 1.0

maxWithOrNull

fun <T> Sequence<T>.maxWithOrNull(comparator: Comparator<in T>): T?

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

Since Kotlin 1.4

min

fun <T : Comparable<T>> Sequence<T>.~~min~~(): T?

Since Kotlin 1.0

fun Sequence<Double>.~~min~~(): Double?

fun Sequence<Float>.~~min~~(): Float?

Since Kotlin 1.1

minBy

inline fun <T, R : Comparable<R>> Sequence<T>.~~minBy~~(selector: (T) -> R): T?

Since Kotlin 1.0

minByOrNull

inline fun <T, R : Comparable<R>> Sequence<T>.minByOrNull(selector: (T) -> R): T?

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

Since Kotlin 1.4

minOf

inline fun <T, R : Comparable<R>> Sequence<T>.minOf(selector: (T) -> R): R

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

inline fun <T> Sequence<T>.minOf(selector: (T) -> Float): Float

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

Since Kotlin 1.4

minOfOrNull

inline fun <T, R : Comparable<R>> Sequence<T>.minOfOrNull(selector: (T) -> R): R?

inline fun <T> Sequence<T>.minOfOrNull(selector: (T) -> Double): Double?

inline fun <T> Sequence<T>.minOfOrNull(selector: (T) -> Float): Float?

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.

Since Kotlin 1.4

minOfWith

inline fun <T, R> Sequence<T>.minOfWith(comparator: Comparator<in R>, selector: (T) -> R): R

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

Since Kotlin 1.4

minOfWithOrNull

inline fun <T, R> Sequence<T>.minOfWithOrNull(comparator: Comparator<in R>, selector: (T) -> R): R?

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.

Since Kotlin 1.4

minOrNull

fun <T : Comparable<T>> Sequence<T>.minOrNull(): T?

fun Sequence<Double>.minOrNull(): Double?

fun Sequence<Float>.minOrNull(): Float?

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

Since Kotlin 1.4

minus

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

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

Since Kotlin 1.0

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 array.

Since Kotlin 1.0

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 collection.

Since Kotlin 1.0

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

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

Since Kotlin 1.0

minusElement

inline fun <T> Sequence<T>.minusElement(element: T): Sequence<T>

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

Since Kotlin 1.0

minWith

fun <T> Sequence<T>.~~minWith~~(comparator: Comparator<in T>): T?

Since Kotlin 1.0

minWithOrNull

fun <T> Sequence<T>.minWithOrNull(comparator: Comparator<in T>): T?

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

Since Kotlin 1.4

none

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

Returns true if the sequence has no elements.

Since Kotlin 1.0

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

Returns true if no elements match the given predicate.

Since Kotlin 1.0

onEach

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

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

Since Kotlin 1.1

onEachIndexed

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

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

Since Kotlin 1.4

orEmpty

inline fun <T> Sequence<T>?.orEmpty(): Sequence<T>

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

Since Kotlin 1.3

partition

inline fun <T> Sequence<T>.partition(predicate: (T) -> Boolean): Pair<List<T>, List<T>>

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.

Since Kotlin 1.0

plus

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

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

Since Kotlin 1.0

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 array.

Since Kotlin 1.0

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 collection.

Since Kotlin 1.0

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

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

Since Kotlin 1.0

plusElement

inline fun <T> Sequence<T>.plusElement(element: T): Sequence<T>

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

Since Kotlin 1.0

reduce

inline fun <S, T : S> Sequence<T>.reduce(operation: (acc: S, T) -> S): S

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

Since Kotlin 1.0

reduceIndexed

inline fun <S, T : S> Sequence<T>.reduceIndexed(operation: (index: Int, acc: S, T) -> S): S

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.

Since Kotlin 1.0

reduceIndexedOrNull

inline fun <S, T : S> Sequence<T>.reduceIndexedOrNull(operation: (index: Int, acc: S, T) -> S): S?

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.

Since Kotlin 1.4

reduceOrNull

inline fun <S, T : S> Sequence<T>.reduceOrNull(operation: (acc: S, T) -> S): S?

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

Since Kotlin 1.4

requireNoNulls

fun <T : Any> Sequence<T?>.requireNoNulls(): Sequence<T>

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

Since Kotlin 1.0

runningFold

fun <T, R> Sequence<T>.runningFold(initial: R, operation: (acc: R, T) -> R): Sequence<R>

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.

Since Kotlin 1.4

runningFoldIndexed

fun <T, R> Sequence<T>.runningFoldIndexed(initial: R, operation: (index: Int, acc: R, T) -> R): Sequence<R>

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.

Since Kotlin 1.4

runningReduce

fun <S, T : S> Sequence<T>.runningReduce(operation: (acc: S, T) -> S): Sequence<S>

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.

Since Kotlin 1.4

runningReduceIndexed

fun <S, T : S> Sequence<T>.runningReduceIndexed(operation: (index: Int, acc: S, T) -> S): Sequence<S>

Since Kotlin 1.4

scan

fun <T, R> Sequence<T>.scan(initial: R, operation: (acc: R, T) -> R): Sequence<R>

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.

Since Kotlin 1.4

scanIndexed

fun <T, R> Sequence<T>.scanIndexed(initial: R, operation: (index: Int, acc: R, T) -> R): Sequence<R>

Since Kotlin 1.4

Sequence

inline fun <T> Sequence(crossinline iterator: () -> Iterator<T>): Sequence<T>

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.

Since Kotlin 1.0

sequence

fun <T> sequence(block: suspend SequenceScope<T>.() -> Unit): Sequence<T>

Builds a Sequence lazily yielding values one by one.

Since Kotlin 1.3

sequenceOf

fun <T> sequenceOf(vararg elements: T): Sequence<T>

Creates a sequence that returns the specified values.

Since Kotlin 1.0

shuffled

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

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

Since Kotlin 1.4

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

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

Since Kotlin 1.4

single

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

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

Since Kotlin 1.0

inline fun <T> Sequence<T>.single(predicate: (T) -> Boolean): T

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

Since Kotlin 1.0

singleOrNull

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

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

Since Kotlin 1.0

inline fun <T> Sequence<T>.singleOrNull(predicate: (T) -> Boolean): T?

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

Since Kotlin 1.0

sorted

fun <T : Comparable<T>> Sequence<T>.sorted(): Sequence<T>

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

Since Kotlin 1.0

sortedBy

inline fun <T, R : Comparable<R>> Sequence<T>.sortedBy(crossinline selector: (T) -> R?): Sequence<T>

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

Since Kotlin 1.0

sortedByDescending

inline fun <T, R : Comparable<R>> Sequence<T>.sortedByDescending(crossinline selector: (T) -> R?): Sequence<T>

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

Since Kotlin 1.0

sortedDescending

fun <T : Comparable<T>> Sequence<T>.sortedDescending(): Sequence<T>

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

Since Kotlin 1.0

sortedWith

fun <T> Sequence<T>.sortedWith(comparator: Comparator<in T>): Sequence<T>

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

Since Kotlin 1.0

sum

@JvmName(name = "sumOfByte")

fun Sequence<Byte>.sum(): Int

@JvmName(name = "sumOfDouble")

fun Sequence<Double>.sum(): Double

@JvmName(name = "sumOfFloat")

fun Sequence<Float>.sum(): Float

@JvmName(name = "sumOfInt")

fun Sequence<Int>.sum(): Int

@JvmName(name = "sumOfLong")

fun Sequence<Long>.sum(): Long

@JvmName(name = "sumOfShort")

fun Sequence<Short>.sum(): Int

Returns the sum of all elements in the sequence.

Since Kotlin 1.0

@JvmName(name = "sumOfUByte")

fun Sequence<UByte>.sum(): UInt

@JvmName(name = "sumOfUInt")

fun Sequence<UInt>.sum(): UInt

@JvmName(name = "sumOfULong")

fun Sequence<ULong>.sum(): ULong

@JvmName(name = "sumOfUShort")

fun Sequence<UShort>.sum(): UInt

Returns the sum of all elements in the sequence.

Since Kotlin 1.5

sumBy

inline fun <T> Sequence<T>.~~sumBy~~(selector: (T) -> Int): Int

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

Since Kotlin 1.0

sumByDouble

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

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

Since Kotlin 1.0

sumOf

@JvmName(name = "sumOfDouble")

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

@JvmName(name = "sumOfInt")

inline fun <T> Sequence<T>.sumOf(selector: (T) -> Int): Int

@JvmName(name = "sumOfLong")

inline fun <T> Sequence<T>.sumOf(selector: (T) -> Long): Long

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

Since Kotlin 1.4

@JvmName(name = "sumOfUInt")

inline fun <T> Sequence<T>.sumOf(selector: (T) -> UInt): UInt

@JvmName(name = "sumOfULong")

inline fun <T> Sequence<T>.sumOf(selector: (T) -> ULong): ULong

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

Since Kotlin 1.5

@JvmName(name = "sumOfBigDecimal")

inline fun <T> Sequence<T>.sumOf(selector: (T) -> BigDecimal): BigDecimal

@JvmName(name = "sumOfBigInteger")

inline fun <T> Sequence<T>.sumOf(selector: (T) -> BigInteger): BigInteger

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

Since Kotlin 1.4

take

fun <T> Sequence<T>.take(n: Int): Sequence<T>

Returns a sequence containing first n elements.

Since Kotlin 1.0

takeWhile

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

Returns a sequence containing first elements satisfying the given predicate.

Since Kotlin 1.0

toCollection

fun <T, C : MutableCollection<in T>> Sequence<T>.toCollection(destination: C): C

Appends all elements to the given destination collection.

Since Kotlin 1.0

toHashSet

fun <T> Sequence<T>.toHashSet(): HashSet<T>

Returns a new HashSet of all elements.

Since Kotlin 1.0

toList

fun <T> Sequence<T>.toList(): List<T>

Returns a List containing all elements.

Since Kotlin 1.0

toMutableList

fun <T> Sequence<T>.toMutableList(): MutableList<T>

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

Since Kotlin 1.0

toMutableSet

fun <T> Sequence<T>.toMutableSet(): MutableSet<T>

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

Since Kotlin 1.0

toSet

fun <T> Sequence<T>.toSet(): Set<T>

Returns a Set of all elements.

Since Kotlin 1.0

toSortedSet

fun <T : Comparable<T>> Sequence<T>.toSortedSet(): SortedSet<T>

fun <T> Sequence<T>.toSortedSet(comparator: Comparator<in T>): SortedSet<T>

Returns a new SortedSet of all elements.

Since Kotlin 1.0

unzip

fun <T, R> Sequence<Pair<T, R>>.unzip(): Pair<List<T>, List<R>>

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.

Since Kotlin 1.0

windowed

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

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.

Since Kotlin 1.2

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

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.

Since Kotlin 1.2

withIndex

fun <T> Sequence<T>.withIndex(): Sequence<IndexedValue<T>>

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

Since Kotlin 1.0

zip

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. The resulting sequence ends as soon as the shortest input sequence ends.

Since Kotlin 1.0

fun <T, R, V> Sequence<T>.zip(other: Sequence<R>, transform: (a: T, b: R) -> V): Sequence<V>

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.

Since Kotlin 1.0

zipWithNext

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

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

Since Kotlin 1.2

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

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

Since Kotlin 1.2

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