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SequenceͱCorou*neͷ
@RyotaMurohoshi
2017/04/04'ୈ5ճ'Kotlinษڧձ'@SanSan
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ࣗݾհ
@RyotaMurohoshi
Kotlin͕͖Ͱ͢ɻC#͖Ͱ͢ɻ
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SequenceͬͯԿʁ
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Sequence
ίϨΫγϣϯΠϯλʔϑΣʔε
public interface Sequence {
public operator fun iterator(): Iterator
}
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SequenceʹɺListArrayͱಉ͡Α͏ʹ
mapfilterͱ͍֦ͬͨு͕ؔ͋Γ·͢
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Ͱڍಈ͕େ͖͘ҧ͍·͢
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Listͷmapɾfilterͷڍಈ
val list : List = listOf(0, 1, 2, 3)
val converted = list
.filter {
println("filter $it")
it.rem(2) == 0
}
.map {
println("map $it")
it
}
println("--------")
for(it in converted) println("for $it")
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Listͷmapɾfilterͷڍಈ
filter 0
filter 1
filter 2
filter 3
map 0
map 2
--------
for 0
for 2
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Listͷmapfilterɺ
શཁૉʹରͯؔ͠Ϧςϥϧ͕ଈ࠲ʹద༻͞Ε·͢
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࣍Sequence
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Sequenceͷmapɾfilterͷڍಈ
val sequence : Sequence = sequenceOf(0, 1, 2, 3)
val converted = sequence
.filter {
println("filter $it")
it.rem(2) == 0
}
.map {
println("map $it")
it
}
println("--------")
for(it in converted) println("for $it")
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--------
filter 0
map 0
for 0
filter 1
filter 2
map 2
for 2
filter 3
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Sequenceͷmapɾfilter
ͦͷཁૉ͕ඞཁʹͳͬͨλΠϛϯάͰ
ؔϦςϥϧ͕ద༻͞Ε·͢
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JavaͷStream)API
C#ͷLINQ
ʹࣅͯ·͢Ͷ
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ʮͰɺ࣮ࡍ͏໘͋Δͷʁʯ
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͋ΔΜͰ͢ʂ
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࣮ࡍʹSequenceͷ׆༂͢Δ໘
• ϑΝΠϧͷ1ߦͣͭಡΈࠐΈ#File.useLines
• σΟϨΫτϦͷϑΝΠϧ୳ࡧ#FireTreeWalk
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ͯ͢࠷ޙ·ͰҰؾʹΔඞཁ͕ͳ͍
ͦ͏͍͏࣌ʹ׆༂
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Sequence͕ͲΜͳͷ͔ɺ
ͲΜͳ໘Ͱ׆༂͢Δ͔Θ͔Γ·ͨ͠Ͷʁ
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࣍ɺ͖ͬ͞ͷfilterͷ࣮ΛݟͯΈ·͠ΐ͏
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Listͷfilterͷ࣮
࣮ࡍʹIterableͷfilter
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୯७ɻͦͷ·Μ·
৽ͨͳArrayListΛ࡞ͬͯɺforͯ͠ɺifͯ͠ɺaddͯ͠
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List(Iterable)ͷfilterͷ࣮
public inline fun Iterable.filter(predicate: (T) -> Boolean): List {
return filterTo(ArrayList(), predicate)
}
public inline fun > Iterable
.filterTo(destination: C, predicate: (T) -> Boolean): C {
for (element in this)
if (predicate(element))
destination.add(element)
return destination
}
h"ps:/
/github.com/JetBrains/kotlin/blob/v1.1.1/libraries/stdlib/src/generated/_Collec=ons.kt>ΑΓ
Πϯσϯτม͍͑ͯ·͢
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୯७ɻͦͷ·Μ·
৽ͨͳArrayListΛ࡞ͬͯɺforͯ͠ɺifͯ͠ɺaddͯ͠
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͡Ό͊ɺSequenceʁ
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Sequenceͷfilterͷ࣮ʁ
public fun Sequence.filter(predicate: (T) -> Boolean): Sequence {
return FilteringSequence(this, true, predicate)
}
h"ps:/
/github.com/JetBrains/kotlin/blob/v1.1.1/libraries/stdlib/src/generated/_Sequences.kt#L307
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;Ή;ΉɻͳΔ΄Ͳɻ
FilteringSequenceͷ࣮ʁ
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FilteringSequenceͷ࣮
internal 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
}
}
}
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͍ʂ
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IteratorΛ࣮͠ͳ͍ͱ͍͚ͳ͍
͘ͳͬͯ͠·͏
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େม
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ࠓͷςʔϚKotlin'1.1
͓ͨͤ͠·ͨ͠
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Kotlin1.1ͰCorou,neಋೖ
(·ͩexperimental͍͍ͬͯͯΔ͚Ͳʂ)
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filterͱಉ༷ͷॲཧɺ͏ʑॻ͔ͳ࣮ͯ͘Ͱ͖Δ
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Corou%neΛͬͯ
SequenceͷfilterΛॻ͘ͱʁ
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Kotlin'1.1ͰSequenceͷfilter
fun Sequence.where(predicate: (T) -> Boolean): Sequence =
buildSequence {
for (element in iterator()) {
if (predicate(element)) {
yield(element)
}
}
}
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buildSequenceʂ
ͦͯ͠yieldʂ
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forͯ͠ifͯ͠
ײతͰ͠ΐʁ
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Kotlin'1.1ͰSequenceͷfilter
fun Sequence.where(predicate: (T) -> Boolean): Sequence =
buildSequence {
for (element in iterator()) {
if (predicate(element)) {
yield(element)
}
}
}
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͜ΕͰSequenceΛ؆୯ʹ࡞ΕΔ
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Generator
ʢͱ͔ݴΘΕͯΔΒ͍͠ʣ
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buildSequenceͷڍಈΛprintlnͰ
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val sequence: Sequence = buildSequence {
println("before A")
yield("A")
println("before B")
yield("B")
println("last")
}
println("-----------")
for (element in sequence) {
println("for $element")
}
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-----------
before A
for A
before B
for B
last
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ϙΠϯτ!தஅ!ͱ!࠶։
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val sequence: Sequence = buildSequence {
println("before A")
yield("A")
println("before B")
yield("B")
println("last")
}
println("-----------")
val iterator = sequence.iterator()
println(iterator.hasNext())
println(iterator.next())
println(iterator.hasNext())
println(iterator.next())
println(iterator.hasNext())
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-----------
before A
true
A
before B
true
B
lastfalse
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GeneratorΛͬͯ
͍Ζ͍Ζ࡞ͬͯΈ·͠ΐ͏
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ແݶUnit
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ແݶUnit
fun infiniteUnitSequence() = buildSequence {
while (true) {
yield(Unit)
}
}
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map
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map
fun Sequence.map(selector: (T) -> R): Sequence =
buildSequence {
for (element in iterator()) {
yield(selector(element))
}
}
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File.useLinesͬΆ͍ͭ
fun sequenceOfLines(fileName: String) = buildSequence {
BufferedReader(FileReader(fileName)).use {
while (true) {
yield(it.readLine() ?: break)
}
}
}
h"ps:/
/github.com/Kotlin/kotlin4corou6nes/blob/master/examples/sequence/sequenceOfLines.kt
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buffer(count,,skip)
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val sequence = sequenceOf(0, 1, 2, 3, 4, 5)
val buffered = sequence.buffer(3, 2)
println(buffered.toList()) // දࣔͷͨΊtoList
//[[0, 1, 2],[2, 3, 4], [4, 5]]
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buffer(count,,skip)
fun Sequence.buffer(count: Int, skip: Int): Sequence> =
buildSequence {
val buffers = LinkedList>()
var i = 0
forEach { element ->
if (i.rem(skip) == 0)
buffers.add(mutableListOf())
for (buffer in buffers)
buffer.add(element)
if (buffers.size > 0 && buffers.peek().count() == count)
yield(buffers.poll().toList())
i++
}
yieldAll(buffers)
}
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Ͷʁ
buildSequenceؔΛ͑؆୯ʹ
SequenceͷؔΛ࡞ΕΔͰ͠ΐʁ
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·ͱΊ
• Sequenceศར
• ͰKotlin01.0ͰSequenceͳϝιουͷ࣮໘
• Kotlin01.1ͰCorou6neՃΘͬͨ
• Corou6neasync0/0await͚ͩ͡Όͳ͍
• buildSequenceͰSequenceͳϝιουͷָ࣮ʹͰ͖Δ
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͕࣌ؒڐ͢ݶΓখωλΛ
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QʮbuildSequenceʁgenerate͡Όͳ͍ͷʁʯ
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A"ͳΜ͔มΘͬͨͬΆ͍Ͱ͢Αɻ
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Kotlin/kotlin)corou-nesͷυΩϡϝϯτ
2017/01/17ͰมΘͬͯ·ͨ͠
h"ps:/
/github.com/Kotlin/kotlin4corou6nes/commit/c8232f0cbff664d232fe46c1a554219c482fe10d
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Q"ʮͲ͏ͬͨΒࢼͤΔͷʁʯ
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A"ʮGenerator(buildSequence)
ՃϥΠϒϥϦ͍Βͳ͍Ͱ͢Αʯ
ͨͩexperimentalͳcorou.neܯࠂग़Δ͔Βɺ੍ϑϥάΛཱ͍ͯͯͩ͘͞Ͷ
h"p:/
/kotlinlang.org/docs/diagnos3cs/experimental7corou3nes.html
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Q"ʮExperimentalͳͷ?ʯ
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A"ʮExperimentalͩͦ͏Ͱ͢ʯ
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Ͳ͏͍͏͜ͱʁ
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KotlinͷExperimentalͷఆٛʹΑΔͱɺ
• 1.1.xͷؒޙํޓੑͷอূ͋Γ
• 1.2Ͱอূͳ͠
h"ps:/
/kotlinlang.org/docs/reference/compa6bility.html#experimental;features
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experimental͔ͩΒύοέʔδ
kotlin.corou+nes.experimental
API͕֬ఆͨ͠Βɺkotlin.corou.nesʹ
(ޙํޓੑͷͨΊkotlin.corou,nes.experimentalΔ)
h"ps:/
/kotlinlang.org/docs/reference/corou6nes.html#experimental:status:of:corou6nes
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Kotlin'1.1ͷϒϩάΑΓ
An#important#note.#With#all#the#benefits#that#they#bring,#Kotlin#
corou9nes#are#a#fairly#new#design#that#needs#extensive#ba?le@
tes9ng#before#we#can#be#sure#it’s#100%#right#and#complete.#This#is#
why#we#will#release#it#under#an#“experimental”#opt@in#flag.#We#do#
not#expect#the#language#rules#to#change,#but#APIs#may#require#
some#adjustments#in#Kotlin#1.2.
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Kotlin'1.1ͷϒϩάΑΓ
We#do#not#expect#the#language#rules#to#change,#but#APIs#may#
require#some#adjustments#in#Kotlin#1.2.
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ͳΔ΄ͲɺมΘΔՄೳੑ͋Δ
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·ͱΊ
• Sequenceศར
• ͰKotlin01.0ͰSequenceͳϝιουͷ࣮໘
• Kotlin01.1ͰCorou6neՃΘͬͨ
• Corou6neasync0/0await͚ͩ͡Όͳ͍
• buildSequenceͰSequenceͳϝιουͷָ࣮ʹͰ͖Δ
• experimental
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·ͣݸਓϥΠϒϥϦ͔ΒΨϯΨϯ͍·͢