3分でわかるSequence

KotlinのSequence処理の流れについて
@Kotlin Fest 2018

Transcript

1. 3෼ͰΘ͔ΔSequence Kotlin Fest 2018 scache @scal_ch CyberAgent, Inc.
2. Sequenceͱ͸ ❖ ListͱࣅͨίϨΫγϣϯૢ࡞͕ՄೳͳΠϯλϑΣʔε ❖ asSequenceͰIterator(List) -> Sequence ʹม׵
3. ྫ (1..100) .map { it * 10 } .filter { it < 825 } .take(2)
4. ྫ (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList()
5. ࠷ऴతʹಘΒΕΔϦετ͸ಉ͡ 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]
6. ListͱSequence ҧ͍͸ʁ
7. ૢ࡞ͷධՁॱ͕ҧ͏ ❖ List͸ઌߦධՁ ❖ Sequence͸஗ԆධՁ
8. List ❖ Collectionૢ࡞(map, filterͳͲ)ͷͨͼʹ৽͍͠ListΛ࡞੒
9. List (1..100) .map { it * 10 } .filter { it < 825 } .take(2)
10. List (1..100) .map { it * 10 } .filter { it < 825 } .take(2)
11. List (1..100) .map { it * 10 } .filter { it < 825 } .take(2) [10, 20, … , 1000]
12. List (1..100) .map { it * 10 } .filter { it < 825 } .take(2) [10, 20, … , 820]
13. List (1..100) .map { it * 10 } .filter { it < 825 } .take(2) [10, 20]
14. Sequence ❖ தؒૢ࡞(map, filterͳͲ)ͱऴ୺ૢ࡞(toListͳͲ)͕͋Δ ❖ ऴ୺ૢ࡞Λߦ͏·Ͱ͸ॲཧ͕࣮ߦ͞Εͳ͍
15. (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList() Sequence
16. (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList() Sequence
17. (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList() Sequence
18. (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList() Sequence
19. (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList() Sequence
20. (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList() Sequence
21. Sequence 1 2 3 … 100 map { it * 10 } filter { it < 825 } take(2) toList()
22. Sequence 1 2 3 … 100 map { it * 10 } 10 filter { it < 825 } take(2) toList()
23. Sequence 1 2 3 … 100 map { it * 10 } 10 filter { it < 825 } ↓ take(2) toList()
24. Sequence 1 2 3 … 100 map { it * 10 } 10 filter { it < 825 } ↓ take(2) ↓ toList()
25. Sequence 1 2 3 … 100 map { it * 10 } 10 filter { it < 825 } ↓ take(2) ↓ toList() 10
26. Sequence 1 2 3 … 100 map { it * 10 } 10 20 filter { it < 825 } ↓ ↓ take(2) ↓ ↓ toList() 10 20
27. Sequence 1 2 3 … 100 map { it * 10 } 10 20 filter { it < 825 } ↓ ↓ take(2) ↓ ↓ toList() 10 20
28. (1..100).asSequence() .map { it * 10 } .filter { it < 825 } .take(2) .toList() Sequence [10, 20]
29. Sequenceͷಛ௃ ❖ ListͱࣅͨίϨΫγϣϯૢ࡞͕Մೳ ❖ தؒ݁ՌͷΦϒδΣΫτΛੜ੒͠ͳ͍ ❖ SequenceΛॲཧ͢ΔϥϜμ͸ΠϯϥΠϯల։͞Εͳ͍ (ListͰ͸Մೳ)
30. Sequence·ͱΊ ❖ ListͱࣅͨίϨΫγϣϯૢ࡞͕Մೳ ❖ தؒ݁ՌͷΦϒδΣΫτΛੜ੒͠ͳ͍ ❖ SequenceΛॲཧ͢ΔϥϜμ͸ΠϯϥΠϯల։͞Εͳ͍ (ListͰ͸Մೳ) ཁૉ਺΍ૢ࡞਺ গ => List ଟ => Sequence
31. Kotlin ͔Θ͍͍ Have a nice Kotlin!
32. ิ଍ ❖ ཁૉ਺͕গͳ͍৔߹͸ɺϥϜμ͕ΠϯϥΠϯԽ͞ΕΔ Listͷํ͕ॲཧ͕ૣ͍ ❖ େ͖ͳϑΝΠϧͷಡΈࠐΈΛߦ͏৔߹͸SequenceΛ࢖͏ ͱྑ͍ ❖ ֦ுؔ਺ BufferedReader.lineSequence()
33. ิ଍ ❖ ListΛ࢖͏΂͖͔SequenceΛ࢖͏΂͖͔͸ɺૢ࡞΍ཁૉ ਺ʹΑͬͯมΘΔͷͰͦͷ࣌ʑʹ൑அ͠·͠ΐ͏