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