FileTreeWalk

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

Use File.walk, File.walkTopDown or File.walkBottomUp extension functions to instantiate a FileTreeWalk instance.

If the file path given is just a file, walker iterates only it. If the file path given does not exist, walker iterates nothing, i.e. it's equivalent to an empty sequence.

Since Kotlin

1.0

Functions

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

Returns true if all elements match the given predicate.

Since Kotlin 1.0
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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
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Creates an Iterable instance that wraps the original sequence returning its elements when being iterated.

Since Kotlin 1.0
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inline fun <T> Sequence<T>.asSequence(): Sequence<T>

Returns this sequence as a Sequence.

Since Kotlin 1.0
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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
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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
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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
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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
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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
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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
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Creates a sequential Stream instance that produces elements from the original sequence.

Since Kotlin 1.2
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@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
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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
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Returns a wrapper sequence that provides values of this sequence, but ensures it can be iterated only one time.

Since Kotlin 1.0
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operator fun <T> Sequence<T>.contains(element: T): Boolean

Returns true if element is found in the sequence.

Since Kotlin 1.0
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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
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Returns a sequence containing only distinct elements from the given sequence.

Since Kotlin 1.0
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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
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fun <T> Sequence<T>.drop(n: Int): Sequence<T>

Returns a sequence containing all elements except first n elements.

Since Kotlin 1.0
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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
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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
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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
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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
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fun <T> Sequence<T>.filter(predicate: (T) -> Boolean): Sequence<T>

Returns a sequence containing only elements matching the given predicate.

Since Kotlin 1.0
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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
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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
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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

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

Since Kotlin 1.0
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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
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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
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Returns a sequence containing all elements that are not null.

Since Kotlin 1.0
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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
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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
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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
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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
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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
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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
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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
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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
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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
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@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
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@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
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@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
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@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
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@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

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

Since Kotlin 1.0
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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
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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
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inline fun <T> Sequence<T>.forEach(action: (T) -> Unit)

Performs the given action on each element.

Since Kotlin 1.0
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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
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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
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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
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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
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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
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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
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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
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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
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open operator override fun iterator(): Iterator<File>

Returns an iterator walking through files.

Since Kotlin 1.0
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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fun <T : Comparable<T>> Sequence<T>.max(): T?
Since Kotlin 1.0
Since Kotlin 1.1
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inline fun <T, R : Comparable<R>> Sequence<T>.maxBy(selector: (T) -> R): T?
Since Kotlin 1.0
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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
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Sets the maximum depth of a directory tree to traverse. By default there is no limit.

Since Kotlin 1.0
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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
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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
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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
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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
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Returns the largest element or null if there are no elements.

Since Kotlin 1.4
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fun <T> Sequence<T>.maxWith(comparator: Comparator<in T>): T?
Since Kotlin 1.0
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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
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fun <T : Comparable<T>> Sequence<T>.min(): T?
Since Kotlin 1.0
Since Kotlin 1.1
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inline fun <T, R : Comparable<R>> Sequence<T>.minBy(selector: (T) -> R): T?
Since Kotlin 1.0
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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
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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
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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
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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
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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
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Returns the smallest element or null if there are no elements.

Since Kotlin 1.4
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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
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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
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fun <T> Sequence<T>.minWith(comparator: Comparator<in T>): T?
Since Kotlin 1.0
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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
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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
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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
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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
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fun onEnter(function: (File) -> Boolean): FileTreeWalk

Sets a predicate function, that is called on any entered directory before its files are visited and before it is visited itself.

Since Kotlin 1.0
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fun onFail(function: (File, IOException) -> Unit): FileTreeWalk

Set a callback function, that is called on a directory when it's impossible to get its file list.

Since Kotlin 1.0
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fun onLeave(function: (File) -> Unit): FileTreeWalk

Sets a callback function, that is called on any left directory after its files are visited and after it is visited itself.

Since Kotlin 1.0
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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
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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
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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
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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
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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
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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
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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
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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
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Returns an original collection containing all the non-null elements, throwing an IllegalArgumentException if there are any null elements.

Since Kotlin 1.0
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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
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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
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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
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fun <S, T : S> Sequence<T>.runningReduceIndexed(operation: (index: Int, acc: S, T) -> S): Sequence<S>

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.

Since Kotlin 1.4
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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
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fun <T, R> Sequence<T>.scanIndexed(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
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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
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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
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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
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Returns a sequence that yields elements of this sequence sorted according to their natural sort order.

Since Kotlin 1.0
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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
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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
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Returns a sequence that yields elements of this sequence sorted descending according to their natural sort order.

Since Kotlin 1.0
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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
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@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
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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
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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
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@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
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fun <T> Sequence<T>.take(n: Int): Sequence<T>

Returns a sequence containing first n elements.

Since Kotlin 1.0
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fun <T> Sequence<T>.takeWhile(predicate: (T) -> Boolean): Sequence<T>

Returns a sequence containing first elements satisfying the given predicate.

Since Kotlin 1.0
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fun <T, C : MutableCollection<in T>> Sequence<T>.toCollection(destination: C): C

Appends all elements to the given destination collection.

Since Kotlin 1.0
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Returns a new HashSet of all elements.

Since Kotlin 1.0
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fun <T> Sequence<T>.toList(): List<T>

Returns a List containing all elements.

Since Kotlin 1.0
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fun <K, V> Sequence<Pair<K, V>>.toMap(): Map<K, V>

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

Since Kotlin 1.0
fun <K, V, M : MutableMap<in K, in V>> Sequence<Pair<K, V>>.toMap(destination: M): M

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

Since Kotlin 1.0
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Returns a new MutableList filled with all elements of this sequence.

Since Kotlin 1.0
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Returns a new MutableSet containing all distinct elements from the given sequence.

Since Kotlin 1.0
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fun <T> Sequence<T>.toSet(): Set<T>

Returns a Set of all elements.

Since Kotlin 1.0
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fun <T> Sequence<T>.toSortedSet(comparator: Comparator<in T>): SortedSet<T>

Returns a new SortedSet of all elements.

Since Kotlin 1.0
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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
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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
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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
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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
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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