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3分でわかるSequence
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scache
August 25, 2018
Programming
1
690
3分でわかるSequence
KotlinのSequence処理の流れについて
@Kotlin Fest 2018
scache
August 25, 2018
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Transcript
3ͰΘ͔ΔSequence Kotlin Fest 2018 scache @scal_ch CyberAgent, Inc.
Sequenceͱ ❖ ListͱࣅͨίϨΫγϣϯૢ࡞͕ՄೳͳΠϯλϑΣʔε ❖ asSequenceͰIterator(List) -> Sequence ʹม
ྫ (1..100) .map { it * 10 } .filter {
it < 825 } .take(2)
ྫ (1..100).asSequence() .map { it * 10 } .filter {
it < 825 } .take(2) .toList()
࠷ऴతʹಘΒΕΔϦετಉ͡ ʢ෭࡞༻ͳ͠ͷ࣌) (1..100) .map { it * 10 } .filter
{ it < 825 } .take(2) (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList() [10, 20]
ListͱSequence ҧ͍ʁ
ૢ࡞ͷධՁॱ͕ҧ͏ ❖ ListઌߦධՁ ❖ SequenceԆධՁ
List ❖ Collectionૢ࡞(map, filterͳͲ)ͷͨͼʹ৽͍͠ListΛ࡞
List (1..100) .map { it * 10 } .filter {
it < 825 } .take(2)
List (1..100) .map { it * 10 } .filter {
it < 825 } .take(2)
List (1..100) .map { it * 10 } .filter {
it < 825 } .take(2) [10, 20, … , 1000]
List (1..100) .map { it * 10 } .filter {
it < 825 } .take(2) [10, 20, … , 820]
List (1..100) .map { it * 10 } .filter {
it < 825 } .take(2) [10, 20]
Sequence ❖ தؒૢ࡞(map, filterͳͲ)ͱऴૢ࡞(toListͳͲ)͕͋Δ ❖ ऴૢ࡞Λߦ͏·Ͱॲཧ͕࣮ߦ͞Εͳ͍
(1..100).asSequence() .map { it * 10 } .filter { it
< 825 } .take(2) .toList() Sequence
(1..100).asSequence() .map { it * 10 } .filter { it
< 825 } .take(2) .toList() Sequence
(1..100).asSequence() .map { it * 10 } .filter { it
< 825 } .take(2) .toList() Sequence
(1..100).asSequence() .map { it * 10 } .filter { it
< 825 } .take(2) .toList() Sequence
(1..100).asSequence() .map { it * 10 } .filter { it
< 825 } .take(2) .toList() Sequence
(1..100).asSequence() .map { it * 10 } .filter { it
< 825 } .take(2) .toList() Sequence
Sequence 1 2 3 … 100 map { it *
10 } filter { it < 825 } take(2) toList()
Sequence 1 2 3 … 100 map { it *
10 } 10 filter { it < 825 } take(2) toList()
Sequence 1 2 3 … 100 map { it *
10 } 10 filter { it < 825 } ↓ take(2) toList()
Sequence 1 2 3 … 100 map { it *
10 } 10 filter { it < 825 } ↓ take(2) ↓ toList()
Sequence 1 2 3 … 100 map { it *
10 } 10 filter { it < 825 } ↓ take(2) ↓ toList() 10
Sequence 1 2 3 … 100 map { it *
10 } 10 20 filter { it < 825 } ↓ ↓ take(2) ↓ ↓ toList() 10 20
Sequence 1 2 3 … 100 map { it *
10 } 10 20 filter { it < 825 } ↓ ↓ take(2) ↓ ↓ toList() 10 20
(1..100).asSequence() .map { it * 10 } .filter { it
< 825 } .take(2) .toList() Sequence [10, 20]
Sequenceͷಛ ❖ ListͱࣅͨίϨΫγϣϯૢ࡞͕Մೳ ❖ தؒ݁ՌͷΦϒδΣΫτΛੜ͠ͳ͍ ❖ SequenceΛॲཧ͢ΔϥϜμΠϯϥΠϯల։͞Εͳ͍ (ListͰՄೳ)
Sequence·ͱΊ ❖ ListͱࣅͨίϨΫγϣϯૢ࡞͕Մೳ ❖ தؒ݁ՌͷΦϒδΣΫτΛੜ͠ͳ͍ ❖ SequenceΛॲཧ͢ΔϥϜμΠϯϥΠϯల։͞Εͳ͍ (ListͰՄೳ) ཁૉૢ࡞ গ
=> List ଟ => Sequence
Kotlin ͔Θ͍͍ Have a nice Kotlin!
ิ ❖ ཁૉ͕গͳ͍߹ɺϥϜμ͕ΠϯϥΠϯԽ͞ΕΔ Listͷํ͕ॲཧ͕ૣ͍ ❖ େ͖ͳϑΝΠϧͷಡΈࠐΈΛߦ͏߹SequenceΛ͏ ͱྑ͍ ❖ ֦ுؔ BufferedReader.lineSequence()
ิ ❖ ListΛ͏͖͔SequenceΛ͏͖͔ɺૢ࡞ཁૉ ʹΑͬͯมΘΔͷͰͦͷ࣌ʑʹஅ͠·͠ΐ͏