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KotlinΒ͍͠ίʔυ
ୈճ͔Θ͍͍,PUMJOษڧձ
!
ຊ,PUMJOϢʔβάϧʔϓ
ᖒଠ!OHTX@UBSP
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ࣗݾհ
w ᖒଠ!OHTX@UBSP
w ࣄͰ+BWB
4DBMB
"OESPJE
w ࣗশ,PUMJOΤϰΝϯδΣϦετ
w ࡀɺֈ࠲ɺͱ͕େ͖
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Έͳ͞Μ
KotlinΒ͍͠ίʔυ
ॻ͍ͯ·͔͢ʁ
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w +BWBܦݧ͋Γˠ,PUMJO؆୯
!
w ؔϦςϥϧɺߴ֊ؔ
w ֦ுؔɺ%FMFHBUFE1SPQFSUZ
w /6--҆શ
KotlinͬΆ͍ίʔυʁ
ػೳଟͯ͘
͍͜ͳͤΜ
ͱݴͬͯʜ
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ຊͷςʔϚ
KotlinΒ͍͠ίʔυ
KotlinͷػೳΛ׆͔ͨ͠ίʔυ
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ࡐ1. sum
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fun sum(xs: List): Int {!
var sum = 0!
for(x in ints) {!
sum += x!
}!
return sum!
}
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fun sum(xs: List): Int {!
var sum = 0!
for(x in ints) {!
sum += x!
}!
return sum!
}
WBSݏͩͳʔ
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int {!
if(xs.isEmpty())!
return a!
else!
return go(xs.drop(1), a + xs.first())!
}!
!
return go(xs, 0)!
}
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int {!
if(xs.isEmpty())!
return a!
else!
return go(xs.drop(1), a + xs.first())!
}!
!
return go(xs, 0)!
}
ඌݺͼग़͠࠷దԽΛ༗ޮ
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int {!
if(xs.isEmpty())!
return a!
else!
return go(xs.drop(1), a + xs.first())!
}!
!
return go(xs, 0)!
}
ϩʔΧϧؔ
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int {!
if(xs.isEmpty())!
return a!
else!
return go(xs.drop(1), a + xs.first())!
}!
!
return go(xs, 0)!
}
JGͰFMTFͰSFUVSO
ؾ࣋ͪѱ͍ʜ
JGͰFMTFͰSFUVSO
ؾ࣋ͪѱ͍ʜ
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int {!
return if(xs.isEmpty()) a!
else go(xs.drop(1), a + xs.first())!
}!
!
return go(xs, 0)!
}
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int {!
return if(xs.isEmpty()) a!
else go(xs.drop(1), a + xs.first())!
}!
!
return go(xs, 0)!
}
JGFMTFࣜ
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int {!
return if(xs.isEmpty()) a!
else go(xs.drop(1), a + xs.first())!
}!
!
return go(xs, 0)!
}
ͬͱ
͔ͬ͜Α͘Ͱ͖Δ
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int =!
if(xs.isEmpty()) a!
else go(xs.drop(1), a + xs.first())!
!
return go(xs, 0)!
}
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fun sum(xs: List): Int {!
@tailRecursive!
fun go(xs: List, a: Int): Int =!
if(xs.isEmpty()) a!
else go(xs.drop(1), a + xs.first())!
!
return go(xs, 0)!
}
୯Ұࣜؔ
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fun sum(xs: List): Int =!
xs.fold(0) { a, x -> a + x }
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fun sum(xs: List): Int =!
xs.fold(0) { a, x -> a + x }
ඪ४"1*
ࠨΈࠐΈ
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fun sum(xs: List): Int =!
xs.fold(0) { a, x -> a + x }
ؔϦςϥϧ
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fun List.sum(): Int =!
fold(0) { a, x -> a + x }
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fun List.sum(): Int =!
fold(0) { a, x -> a + x }
֦ுؔ
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No content
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(sumͳΜ͔ࣗ࡞͠ͳ͍)
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!
!
ඪ४API
fun Iterable.sum(): Int
(sumͳΜ͔ࣗ࡞͠ͳ͍)
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ࡐ1. sum ·ͱΊ
w WBSݏͩ
w UBJM3FDVSTJWFͰ5$0
w ϩʔΧϧؔ
w JGFMTFࣜ
w GVOIPHF
Ͱ୯Ұࣜؔ
w ֦ுؔ
w ඪ४"1*Λ͏
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ࡐ2. nullable
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// ໊લΛऔಘͰ͖Δ!
fun getName(): String?!
!
// อଘͰ͖Δ!
fun save(s: String): Unit
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val name: String? = getName()!
if(name != null) {!
save(name)!
}
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val name: String? = getName()!
if(name != null) {!
save(name)!
}
OVMMνΣοΫ
͜ͷதͰOBNF
OPU/VMMͱͯ͠ѻ͑Δ
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name?.let {!
name -> save(name)!
}
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name?.let {!
name -> save(name)!
}
ඪ४"1*
MFUؔ
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name?.let {!
name -> save(name)!
}
ඪ४"1*
MFUؔ
҆શݺͼग़͠
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name?.let {!
save(it)!
}
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name?.let {!
save(it)!
}
҉ͷม
JU
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name?.let(::save)
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name?.let(::save)
ؔࢀর
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ࡐ2. nullable ·ͱΊ
w OVMMνΣοΫ͍͢͝
w ͷ҆શݺͼग़͠ศར
w MFUؔ໘ന͍
w ҉ͷมJU
w ؔࢀর
w ͓·͚IUUQTTQFBLFSEFDLDPNOUBSP
LPUMJOOVNCFSTIJCVJHVKWN
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ࡐ3. immutable
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class User(id: Long, name: String) {!
val id = id!
val name = name!
!
class Builder {!
var id: Long? = null!
var name: String? = null!
!
fun id(id: Long): Builder {!
this.id = id!
return this!
}!
!
fun name(name: String): Builder {!
this.name = name!
return this!
}!
!
fun build(): User {!
val id = checkNotNull(id)!
val name = checkNotNull(name)!
return User(id, name)!
}!
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val taro = User.Builder()!
.id(123)!
.name(“Taro”)!
! .build()!
!
val jiro = taro.builder()!
.name(“Jiro”)!
.build()
qVFOUJOUFSGBDFͰ
JNNVUBCMFͳͭ
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data class User(!
val id: Long,!
val name: String!
)
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data class User(!
val id: Long,!
val name: String!
)
EBUBΞϊςʔγϣϯ
ϓϩύςΟ
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val taro = User(id=123, name=“Taro”)!
!
val jiro = taro.copy(name=“Jiro”)
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val taro = User(id=123, name=“Taro”)!
!
val jiro = taro.copy(name=“Jiro”)
໊લ͖Ҿ
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val taro = User(id=123, name=“Taro”)!
!
val jiro = taro.copy(name=“Jiro”)
EBUBΞϊςʔγϣϯʹΑΔ
DPQZϝιου
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ࡐ3. immutable ·ͱΊ
w EBUBΞϊςʔγϣϯڧ͍
w ໊લ͖Ҿ
w ˢ͏-PNCPLܥ#VJMEFSύλʔϯཁΒͳ͍
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ࡐ4. decorator
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class GreetableCharSeq!
(private val cs: CharSequence): CharSequence {!
!
fun hello() {!
println("Hello, ${cs}")!
}!
!
override fun length(): Int = cs.length()!
override fun charAt(index: Int): Char = cs.charAt(index)!
override fun subSequence(start: Int, end: Int): CharSequence =!
cs.subSequence(start, end)!
}
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class GreetableCharSeq!
(private val cs: CharSequence): CharSequence {!
!
fun hello() {!
println("Hello, ${cs}")!
}!
!
override fun length(): Int = cs.length()!
override fun charAt(index: Int): Char = cs.charAt(index)!
override fun subSequence(start: Int, end: Int): CharSequence =!
cs.subSequence(start, end)!
}
$IBS4FRVFODFʹ
IFMMPϝιουͷՃ͕͍ͨ͠
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class GreetableCharSeq!
(private val cs: CharSequence): CharSequence {!
!
fun hello() {!
println("Hello, ${cs}")!
}!
!
override fun length(): Int = cs.length()!
override fun charAt(index: Int): Char = cs.charAt(index)!
override fun subSequence(start: Int, end: Int): CharSequence =!
cs.subSequence(start, end)!
}
ͦͷଞͷϝιου
ͦͷ··ϥοϓͯ͠Δ࣮ʹ
ҕৡ
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class GreetableCharSeq!
(private val cs: CharSequence): CharSequence by cs {!
fun hello() {!
println("Hello, ${cs}")!
}!
}
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class GreetableCharSeq!
(private val cs: CharSequence): CharSequence by cs {!
fun hello() {!
println("Hello, ${cs}")!
}!
}
CZͰҕৡ
ҕৡ͢Δ͚ͩͷ
ϝιουهड़ෆཁ
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࣮ࡍ…
fun CharSequence.hello() {!
println(“Hello, $this”)!
}
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ࡐ4. decorator ·ͱΊ
w EFDPSBUPSύλʔϯΈ͍ͨͳͷ͍ͨ͠ͱ͖
CZΩʔϫʔυʹΑΔҕৡͷΈΛ͏
w ࠓճͷྫͰ֦ுؔͰࡁΜͩ
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͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠