kotlin.collections.Sequence.kt Maven / Gradle / Ivy
package kotlin
import java.util.*
import kotlin.support.AbstractIterator
deprecated("Use Sequence instead.")
public interface Stream {
/**
* Returns an iterator that returns the values from the sequence.
*/
public fun iterator(): Iterator
}
/**
* A sequence that returns values through its iterator. The values are evaluated lazily, and the sequence
* is potentially infinite.
*
* @param T the type of elements in the sequence.
*/
public interface Sequence : Stream
/**
* Converts a stream to a sequence.
*/
public fun Stream.toSequence(): Sequence = object : Sequence {
override fun iterator(): Iterator = [email protected]()
}
deprecated("Use sequenceOf() instead", ReplaceWith("sequenceOf(*elements)"))
public fun streamOf(vararg elements: T): Stream = elements.stream()
deprecated("Use sequenceOf() instead", ReplaceWith("sequenceOf(progression)"))
public fun streamOf(progression: Progression): Stream = object : Stream {
override fun iterator(): Iterator = progression.iterator()
}
/**
* Creates a sequence that returns all values from this iterator. The sequence is constrained to be iterated only once.
*/
public fun Iterator.asSequence(): Sequence {
val iteratorSequence = object : Sequence {
override fun iterator(): Iterator = this@asSequence
}
return iteratorSequence.constrainOnce()
}
deprecated("Use asSequence() instead.", ReplaceWith("asSequence()"))
public fun Iterator.sequence(): Sequence = asSequence()
/**
* Creates a sequence that returns all values from this enumeration. The sequence is constrained to be iterated only once.
*/
public fun Enumeration.asSequence(): Sequence = this.iterator().asSequence()
/**
* Creates a sequence that returns the specified values.
*/
public fun sequenceOf(vararg elements: T): Sequence = if (elements.isEmpty()) emptySequence() else elements.asSequence()
/**
* Creates a sequence that returns all values in the specified [progression].
*/
public fun sequenceOf(progression: Progression): Sequence = object : Sequence {
override fun iterator(): Iterator = progression.iterator()
}
/**
* Returns an empty sequence.
*/
public fun emptySequence(): Sequence = EmptySequence
private object EmptySequence : Sequence {
override fun iterator(): Iterator = EmptyIterator
}
deprecated("Use FilteringSequence instead")
public class FilteringStream(stream: Stream, sendWhen: Boolean = true, predicate: (T) -> Boolean)
: Stream by FilteringSequence(stream.toSequence(), sendWhen, predicate)
/**
* A sequence that returns the values from the underlying [sequence] that either match or do not match
* the specified [predicate].
*
* @param sendWhen If `true`, values for which the predicate returns `true` are returned. Otherwise,
* values for which the predicate returns `false` are returned
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.filter() or sequence.filterNot() instead.")
public class FilteringSequence(private val sequence: Sequence,
private val sendWhen: Boolean = true,
private val predicate: (T) -> Boolean
) : Sequence {
override fun iterator(): Iterator = object : Iterator {
val iterator = sequence.iterator();
var nextState: Int = -1 // -1 for unknown, 0 for done, 1 for continue
var nextItem: T? = null
private fun calcNext() {
while (iterator.hasNext()) {
val item = iterator.next()
if (predicate(item) == sendWhen) {
nextItem = item
nextState = 1
return
}
}
nextState = 0
}
override fun next(): T {
if (nextState == -1)
calcNext()
if (nextState == 0)
throw NoSuchElementException()
val result = nextItem
nextItem = null
nextState = -1
return result as T
}
override fun hasNext(): Boolean {
if (nextState == -1)
calcNext()
return nextState == 1
}
}
}
deprecated("Use TransformingSequence instead")
public class TransformingStream(stream: Stream, transformer: (T) -> R)
: Stream by TransformingSequence(stream.toSequence(), transformer)
/**
* A sequence which returns the results of applying the given [transformer] function to the values
* in the underlying [sequence].
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.map() instead.")
public class TransformingSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.map(transformer)"))
(private val sequence: Sequence, private val transformer: (T) -> R) : Sequence {
override fun iterator(): Iterator = object : Iterator {
val iterator = sequence.iterator()
override fun next(): R {
return transformer(iterator.next())
}
override fun hasNext(): Boolean {
return iterator.hasNext()
}
}
}
deprecated("Use TransformingIndexedSequence instead")
public class TransformingIndexedStream(stream: Stream, transformer: (Int, T) -> R)
: Stream by TransformingIndexedSequence(stream.toSequence(), transformer)
/**
* A sequence which returns the results of applying the given [transformer] function to the values
* in the underlying [sequence], where the transformer function takes the index of the value in the underlying
* sequence along with the value itself.
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.mapIndexed() instead.")
public class TransformingIndexedSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.mapIndexed(transformer)"))
(private val sequence: Sequence, private val transformer: (Int, T) -> R) : Sequence {
override fun iterator(): Iterator = object : Iterator {
val iterator = sequence.iterator()
var index = 0
override fun next(): R {
return transformer(index++, iterator.next())
}
override fun hasNext(): Boolean {
return iterator.hasNext()
}
}
}
deprecated("Use IndexingSequence instead")
public class IndexingStream(stream: Stream)
: Stream> by IndexingSequence(stream.toSequence())
/**
* A sequence which combines values from the underlying [sequence] with their indices and returns them as
* [IndexedValue] objects.
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.withIndex() instead.")
public class IndexingSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.withIndex()"))
(private val sequence: Sequence) : Sequence> {
override fun iterator(): Iterator> = object : Iterator> {
val iterator = sequence.iterator()
var index = 0
override fun next(): IndexedValue {
return IndexedValue(index++, iterator.next())
}
override fun hasNext(): Boolean {
return iterator.hasNext()
}
}
}
deprecated("Use MergingSequence instead")
public class MergingStream(stream1: Stream, stream2: Stream, transform: (T1, T2) -> V)
: Stream by MergingSequence(stream1.toSequence(), stream2.toSequence(), transform)
/**
* A sequence which takes the values from two parallel underlying sequences, passes them to the given
* [transform] function and returns the values returned by that function. The sequence stops returning
* values as soon as one of the underlying sequences stops returning values.
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.merge() instead.")
public class MergingSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence1.merge(sequence2, transform)"))
(private val sequence1: Sequence,
private val sequence2: Sequence,
private val transform: (T1, T2) -> V
) : Sequence {
override fun iterator(): Iterator = object : Iterator {
val iterator1 = sequence1.iterator()
val iterator2 = sequence2.iterator()
override fun next(): V {
return transform(iterator1.next(), iterator2.next())
}
override fun hasNext(): Boolean {
return iterator1.hasNext() && iterator2.hasNext()
}
}
}
deprecated("Use FlatteningSequence instead")
public class FlatteningStream(stream: Stream, transformer: (T) -> Stream)
: Stream by FlatteningSequence(stream.toSequence(), { transformer(it).toSequence() })
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.flatMap() instead.")
public class FlatteningSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.flatMap(transformer)"))
(private val sequence: Sequence,
private val transformer: (T) -> Sequence
) : Sequence {
override fun iterator(): Iterator = object : Iterator {
val iterator = sequence.iterator()
var itemIterator: Iterator? = null
override fun next(): R {
if (!ensureItemIterator())
throw NoSuchElementException()
return itemIterator!!.next()
}
override fun hasNext(): Boolean {
return ensureItemIterator()
}
private fun ensureItemIterator(): Boolean {
if (itemIterator?.hasNext() == false)
itemIterator = null
while (itemIterator == null) {
if (!iterator.hasNext()) {
return false
} else {
val element = iterator.next()
val nextItemIterator = transformer(element).iterator()
if (nextItemIterator.hasNext()) {
itemIterator = nextItemIterator
return true
}
}
}
return true
}
}
}
deprecated("Use MultiSequence instead")
public class Multistream(stream: Stream>)
: Stream by FlatteningSequence(stream.toSequence(), { it.toSequence() })
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.flatten() instead.")
public class MultiSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.flatten()"))
(private val sequence: Sequence>) : Sequence {
override fun iterator(): Iterator = object : Iterator {
val iterator = sequence.iterator()
var itemIterator: Iterator? = null
override fun next(): T {
if (!ensureItemIterator())
throw NoSuchElementException()
return itemIterator!!.next()
}
override fun hasNext(): Boolean {
return ensureItemIterator()
}
private fun ensureItemIterator(): Boolean {
if (itemIterator?.hasNext() == false)
itemIterator = null
while (itemIterator == null) {
if (!iterator.hasNext()) {
return false
} else {
val element = iterator.next()
val nextItemIterator = element.iterator()
if (nextItemIterator.hasNext()) {
itemIterator = nextItemIterator
return true
}
}
}
return true
}
}
}
deprecated("Use TakeSequence instead")
public class TakeStream(stream: Stream, count: Int)
: Stream by TakeSequence(stream.toSequence(), count)
/**
* A sequence that returns at most [count] values from the underlying [sequence], and stops returning values
* as soon as that count is reached.
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.take() instead.")
public class TakeSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.take(count)"))
(private val sequence: Sequence,
private val count: Int
) : Sequence {
init {
require (count >= 0) { throw IllegalArgumentException("count should be non-negative, but is $count") }
}
override fun iterator(): Iterator = object : Iterator {
var left = count
val iterator = sequence.iterator();
override fun next(): T {
if (left == 0)
throw NoSuchElementException()
left--
return iterator.next()
}
override fun hasNext(): Boolean {
return left > 0 && iterator.hasNext()
}
}
}
deprecated("Use TakeWhileSequence instead")
public class TakeWhileStream(stream: Stream, predicate: (T) -> Boolean) : Stream by TakeWhileSequence(stream.toSequence(), predicate)
/**
* A sequence that returns values from the underlying [sequence] while the [predicate] function returns
* `true`, and stops returning values once the function returns `false` for the next element.
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.takeWhile() instead.")
public class TakeWhileSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.takeWhile(predicate)"))
(private val sequence: Sequence,
private val predicate: (T) -> Boolean
) : Sequence {
override fun iterator(): Iterator = object : Iterator {
val iterator = sequence.iterator();
var nextState: Int = -1 // -1 for unknown, 0 for done, 1 for continue
var nextItem: T? = null
private fun calcNext() {
if (iterator.hasNext()) {
val item = iterator.next()
if (predicate(item)) {
nextState = 1
nextItem = item
return
}
}
nextState = 0
}
override fun next(): T {
if (nextState == -1)
calcNext() // will change nextState
if (nextState == 0)
throw NoSuchElementException()
val result = nextItem as T
// Clean next to avoid keeping reference on yielded instance
nextItem = null
nextState = -1
return result
}
override fun hasNext(): Boolean {
if (nextState == -1)
calcNext() // will change nextState
return nextState == 1
}
}
}
deprecated("Use DropSequence instead")
public class DropStream(stream: Stream, count: Int)
: Stream by DropSequence(stream.toSequence(), count)
/**
* A sequence that skips the specified number of values from the underlying [sequence] and returns
* all values after that.
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.drop() instead.")
public class DropSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.drop(count)"))
(private val sequence: Sequence,
private val count: Int
) : Sequence {
init {
require (count >= 0) { throw IllegalArgumentException("count should be non-negative, but is $count") }
}
override fun iterator(): Iterator = object : Iterator {
val iterator = sequence.iterator();
var left = count
// Shouldn't be called from constructor to avoid premature iteration
private fun drop() {
while (left > 0 && iterator.hasNext()) {
iterator.next()
left--
}
}
override fun next(): T {
drop()
return iterator.next()
}
override fun hasNext(): Boolean {
drop()
return iterator.hasNext()
}
}
}
deprecated("Use DropWhileSequence instead")
public class DropWhileStream(stream: Stream, predicate: (T) -> Boolean) : Stream by DropWhileSequence(stream.toSequence(), predicate)
/**
* A sequence that skips the values from the underlying [sequence] while the given [predicate] returns `true` and returns
* all values after that.
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use sequence.dropWhile() instead.")
public class DropWhileSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence.dropWhile(predicate)"))
(private val sequence: Sequence,
private val predicate: (T) -> Boolean
) : Sequence {
override fun iterator(): Iterator = object : Iterator {
val iterator = sequence.iterator();
var dropState: Int = -1 // -1 for not dropping, 1 for nextItem, 0 for normal iteration
var nextItem: T? = null
private fun drop() {
while (iterator.hasNext()) {
val item = iterator.next()
if (!predicate(item)) {
nextItem = item
dropState = 1
return
}
}
dropState = 0
}
override fun next(): T {
if (dropState == -1)
drop()
if (dropState == 1) {
val result = nextItem as T
nextItem = null
dropState = 0
return result
}
return iterator.next()
}
override fun hasNext(): Boolean {
if (dropState == -1)
drop()
return dropState == 1 || iterator.hasNext()
}
}
}
deprecated("Use DistinctSequence instead and remove with streams.")
private class DistinctStream(private val source: Stream, private val keySelector : (T) -> K) : Stream by DistinctSequence(source.toSequence(), keySelector)
private class DistinctSequence(private val source : Sequence, private val keySelector : (T) -> K) : Sequence {
override fun iterator(): Iterator = DistinctIterator(source.iterator(), keySelector)
}
private class DistinctIterator(private val source : Iterator, private val keySelector : (T) -> K) : AbstractIterator() {
private val observed = HashSet()
override fun computeNext() {
while (source.hasNext()) {
val next = source.next()
val key = keySelector(next)
if (observed.add(key)) {
setNext(next)
return
}
}
done()
}
}
/**
* A sequence which repeatedly calls the specified [producer] function and returns its return values, until
* `null` is returned from [producer].
*/
deprecated("This class is an implementation detail and shall be made internal soon. Use function sequence(nextFunction: () -> T?) instead.")
public class FunctionSequence
deprecated("This class is an implementation detail and shall be made internal soon.", ReplaceWith("sequence(producer)"))
(private val producer: () -> T?) : Sequence {
override fun iterator(): Iterator = object : Iterator {
var nextState: Int = -1 // -1 for unknown, 0 for done, 1 for continue
var nextItem: T? = null
private fun calcNext() {
val item = producer()
if (item == null) {
nextState = 0
} else {
nextState = 1
nextItem = item
}
}
override fun next(): T {
if (nextState == -1)
calcNext()
if (nextState == 0)
throw NoSuchElementException()
val result = nextItem as T
// Clean next to avoid keeping reference on yielded instance
nextItem = null
nextState = -1
return result
}
override fun hasNext(): Boolean {
if (nextState == -1)
calcNext()
return nextState == 1
}
}
}
private class GeneratorSequence(private val getInitialValue: () -> T?, private val getNextValue: (T) -> T?): Sequence {
override fun iterator(): Iterator = object : Iterator {
var nextItem: T? = getInitialValue()
var nextState: Int = if (nextItem == null) 0 else 1 // -1 for unknown, 0 for done, 1 for continue
private fun calcNext() {
nextItem = getNextValue(nextItem!!)
nextState = if (nextItem == null) 0 else 1
}
override fun next(): T {
if (nextState == -1)
calcNext()
if (nextState == 0)
throw NoSuchElementException()
val result = nextItem as T
// Clean next to avoid keeping reference on yielded instance
// need to keep state
// nextItem = null
nextState = -1
return result
}
override fun hasNext(): Boolean {
if (nextState == -1)
calcNext()
return nextState == 1
}
}
}
/**
* Returns a wrapper sequence that provides values of this sequence, but ensures it can be iterated only one time.
*
* [IllegalStateException] is thrown on iterating the returned sequence from the second time.
*/
public fun Sequence.constrainOnce(): Sequence {
// as? does not work in js
//return this as? ConstrainedOnceSequence ?: ConstrainedOnceSequence(this)
return if (this is ConstrainedOnceSequence) this else ConstrainedOnceSequence(this)
}
/**
* Returns a sequence which invokes the function to calculate the next value on each iteration until the function returns `null`.
*
* Returned sequence is constrained to be iterated only once.
*
* @see constrainOnce
*/
public fun sequence(nextFunction: () -> T?): Sequence {
return GeneratorSequence(nextFunction, { nextFunction() }).constrainOnce()
}
deprecated("Use sequence() instead", ReplaceWith("sequence(nextFunction)"))
public fun stream(nextFunction: () -> T?): Sequence = sequence(nextFunction)
/**
* Returns a sequence which invokes the function to calculate the next value based on the previous one on each iteration
* until the function returns `null`. The sequence starts with the specified [initialValue].
*
* The sequence can be iterated multiple times, each time starting with the [initialValue].
*/
public /*inline*/ fun sequence(initialValue: T, nextFunction: (T) -> T?): Sequence =
GeneratorSequence({ initialValue }, nextFunction)
/**
* Returns a sequence which invokes the function [initialValueFunction] to get the first item and then
* [nextFunction] to calculate the next value based on the previous one on each iteration
* until the function returns `null`. The sequence starts with the value returned by [initialValueFunction].
*/
public fun sequence(initialValueFunction: () -> T?, nextFunction: (T) -> T?): Sequence =
GeneratorSequence(initialValueFunction, nextFunction)
deprecated("Use sequence() instead", ReplaceWith("sequence(initialValue, nextFunction)"))
public /*inline*/ fun stream(initialValue: T, nextFunction: (T) -> T?): Sequence = sequence(initialValue, nextFunction)
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