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݄ौ୩+7.
ᖒଠ!OHTX@UBSP
,PUMJO
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+7.ݴޠʂ
Նൃදʂ
+FU#SBJOTʂ
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੩తܕ͚
/6--҆શ
ΦϒδΣΫτࢦ
Ϋϩʔδϟ
γϯϓϧ
BMU+4
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ࠓ͢͜ͱʂ
֦ுؔ
/6--҆શ
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֦ுؔ
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fun main(args : Array) {
"world".hello() /
/ => Hello, world!
}
!
fun String.hello() {
println("Hello, ${this}!")
}
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/
/ Kotlin
fun String.hello() {
println("Hello, ${this}!")
}
!
/
/ Java
static void hello(String receiver) {...}
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/6--҆શ
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val a: String = null /
/ NG
val b: String? = null /
/ OK
/PU/VMM/VMMBCMF
Λ໌֬ʹ۠ผ͢Δ
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val a: String? = null
a.toUpperCase() /
/ NG
/VMMBCMFมʹ
ී௨ʹΞΫηεͰ͖ͳ͍
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val a: String? = null
a?.toUpperCase()
/
/ a.map(String::toUpperCase);
Ͱ҆શݺͼग़͠
Ϩγʔό͕OVMMͳΒOVMMΛฦ͚ͩ͢
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val a: String? = null
a ?: ""
/
/ a.orElse("");
ͰσϑΥϧτ
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val a: String? = null
a!! /
/ !!!Exception!!!
/
/ a.get();
Ͱڧ੍/PU/VMMԽ
ةݥʂݪଇېࢭʂ
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֦ுؔ/6--҆શ
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֦ுؔMFU͜ͳ͢
MFUඪ४ϥΠϒϥϦͷؔ
w JG1SFTFOU
w NBQ
w qBU.BQ
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w JG1SFTFOU
w NBQ
w qBU.BQ
,PUMJOʹWPJE
ͳ͘ɺؔ
ඞͣΛฦ͔͢
Βಉ͡
֦ுؔMFU͜ͳ͢
MFUඪ४ϥΠϒϥϦͷؔ
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w JG1SFTFOU
w NBQ
w qBU.BQ
ʮOVMMͷOVMMʯͱ
͍͏ೖΕࢠߏʹ
ͳΒͳ͍͔Βಉ͡
֦ுؔMFU͜ͳ͢
MFUඪ४ϥΠϒϥϦͷؔ
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a?.let { a -> toInt(a) }
a?.let { toInt(it) }
a?.let(::toInt)
MFU༻ྫ
ಉ͡ɻ
ॻ͖ํ͕ҧ
͏͚ͩ
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ෳͷ/VMMBCMFΛ
/PU/VMMͱͯ͠ѻ͍͍ͨ
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a?.let { a ->
b?.let { b ->
a - b
}
}
ͭͷ*OU B
CͷҾ͖ࢉ
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a?.let { a ->
b?.let { b ->
a - b
}
}
ͭͷ*OU B
CͷҾ͖ࢉ
ωετ
ಡΈʹ͍͘
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/
/ Ҿ͖ࢉͷؔ ΧϦʔԽ
val minus = fun(a: Int) = fun(b: Int) = a - b
!
Ҿͱͯ͠/VMMBCMFͳؔΛऔΕΔMFUతͳͭ
fun A.bind(f: ((A) -> B)?): B? = f?.invoke(this)
ͭͷؔΛ༻ҙ
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b?.bind(a?.bind(minus))
ωετ͕ফ͑ͨʂ
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ωετ͕ফ͑ͨʂ
ׅހͷରԠؔͱ͔͆
BCͳͷʹɺొ͢Δॱং͕ٯɻ
ಡΈʹ͍͘ʂ
b?.bind(a?.bind(minus))
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minus.apply(a)?.apply(b)
Ͱ͖ͨʂ
NJOVT͔Βελʔτͯ͠ɺBɺC
ͷॱͰهड़Ͱ͖Δʂ
ϝιουνΣʔϯʹͳͬͯΔʂ
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ෳࡶ
໘͍͘͞
val minus = fun(a: Int) = fun(b: Int) = a - b
fun A.bind(f: ((A) -> B)?): B? = f?.invoke(this)
fun ((A)->B).apply(a: A?): B? = a?.bind(this)
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if (a != null && b != null) a - b
else null
࣮͜Ε͚ͩͰ͓̺
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࣮͜Ε͚ͩͰ͓̺
OVMMͰͳ͍͜ͱ͕อূ͞ΕΔॴͰ
/VMMBCMFมΛ/PU/VMMͱͯ͠ѻ͑Δ
if (a != null && b != null) a - b
else null
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·ͱΊ
֦ுؔͰศརϝιου͕ੜͤΔʂ
/6--҆શ҆શͰѻ͍ํ؆୯ʂ
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ࣗݾհ
ᖒଠ!OHTX@UBSP
ͱ͕େ͖ͳΤϯδχΞ
4PGUXBSF%FTJHO ٕධ
Ͱ
,PUMJOهࣄΛ࿈ࡌத
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%SPJE,BJHJ
,PUMJO"OESPJE։ൃαϙʔτ
ྗೖΕͯΔײ 1MVHJOϥΠϒϥϦͳͲ
ͷ%SPJE,BJHJͰൃද͠·͢
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͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ
-FU`TFOKPZ,PUMJO