Android with Functional Programming

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"OESPJEXJUI 'VODUJPOBM1SPHSBNNJOH !UBLBTG[ $"54.&&561

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ؔ਺ܕϓϩάϥϛϯάͬͯԿʁ

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ؔ਺ܕϓϩάϥϛϯάͱ͸ 'VODUJPOBMDPEFJTDIBSBDUFSJTFECZPOFUIJOHUIFBCTFODFPG TJEFFGGFDUT*UEPFTO`USFMZPOEBUBPVUTJEFUIFDVSSFOU GVODUJPO BOEJUEPFTO`UDIBOHFEBUBUIBUFYJTUTPVUTJEFUIF DVSSFOUGVODUJPO&WFSZPUIFSlGVODUJPOBMzUIJOHDBOCFEFSJWFE GSPNUIJTQSPQFSUZ "OJOUSPEVDUJPOUPGVODUJPOBMQSPHSBNNJOH IUUQTDPEFXPSETSFDVSTFDPNJTTVFTPOFBOJOUSPEVDUJPOUPGVODUJPOBMQSPHSBNNJOH

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ؔ਺ܕϓϩάϥϛϯάͱ͸ w ෭࡞༻͕ͳ͍͜ͱ w ݱࡏͷؔ਺ͷ֎ʹଘࡏ͢ΔσʔλʹཔΒͣ ɺ  ݱࡏͷؔ਺ͷ֎ʹଘࡏ͢ΔσʔλΛมߋ͠ͳ͍ w ͦͷଞͷʮؔ਺ܕʯͳ΋ͷ͸͢΂ͯɺ͜ͷಛੑͷ೿ੜͰ͋Δ w ෆมσʔλɺୈҰڃؔ਺ɺΧϦʔԽɺߴ֊ؔ਺ɺͳͲ "OJOUSPEVDUJPOUPGVODUJPOBMQSPHSBNNJOH IUUQTDPEFXPSETSFDVSTFDPNJTTVFTPOFBOJOUSPEVDUJPOUPGVODUJPOBMQSPHSBNNJOH

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var num: Int = 0 fun incrementNum() { num += 1 } ෭࡞༻ͷ͋Δؔ਺

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var num: Int = 0 fun incrementNum() { num += 1 } ෭࡞༻ͷ͋Δؔ਺ ؔ਺ͷ֎ʹଘࡏ͢ΔσʔλΛ ؔ਺ͷத͔Βࢀর͍ͯ͠Δ

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var num: Int = 0 fun incrementNum() { num += 1 } ෭࡞༻ͷ͋Δؔ਺ ؔ਺ͷ֎ʹଘࡏ͢ΔσʔλΛ ؔ਺ͷத͔Βมߋ͍ͯ͠Δ

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fun incrementNum(num: Int): Int { return num + 1 } ෭࡞༻ͷͳ͍ؔ਺

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fun incrementNum(num: Int): Int { return num + 1 } ෭࡞༻ͷͳ͍ؔ਺ ؔ਺ͷ֎ʹଘࡏ͢ΔσʔλΛ ؔ਺ͷத͔Β௚઀ࢀর͠ͳ͍

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fun incrementNum(num: Int): Int { return num + 1 } ෭࡞༻ͷͳ͍ؔ਺ ؔ਺ͷ֎ʹଘࡏ͢ΔσʔλΛ ؔ਺ͷத͔Β௚઀มߋ͠ͳ͍

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fun KeirinCup.isHeld(): Boolean { return this.startDate.isBefore(LocalDate.now()) && this.endDate.isAfter(LocalDate.now()) } ෭࡞༻ͷ͋Δؔ਺

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fun KeirinCup.isHeld(): Boolean { return this.startDate.isBefore(LocalDate.now()) && this.endDate.isAfter(LocalDate.now()) } ෭࡞༻ͷ͋Δؔ਺ ؔ਺ͷ֎ʹଘࡏ͢ΔσʔλΛ ࢀর͍ͯ͠Δ

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fun KeirinCup.isHeld(now: LocalDate): Boolean { return this.startDate.isBefore(now) && this.endDate.isAfter(now) } ෭࡞༻ͷͳ͍ؔ਺

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fun KeirinCup.isHeld(now: LocalDate): Boolean { return this.startDate.isBefore(now) && this.endDate.isAfter(now) } ෭࡞༻ͷͳ͍ؔ਺ ؔ਺ͷ֎ʹଘࡏ͢ΔσʔλΛ ࢀর͠ͳ͍

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fun divide(x: Double, y: Double): Double { if (y == 0.0) { throw IllegalArgumentException() } return x / y } ෭࡞༻ͷ͋Δؔ਺ʁ

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fun divide(x: Double, y: Double): Double { if (y == 0.0) { throw IllegalArgumentException() } return x / y } ෭࡞༻ͷ͋Δؔ਺ʁ ྫ֎͕ൃੜ͢Δͱɺؔ਺ͷ֎ͷঢ়ଶ͕มԽ͢Δ ෭࡞༻͕͋Δ

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fun divide(x: Double, y: Double): Double { if (y == 0.0) { return Double.NaN } return x / y } ෭࡞༻ͷͳ͍ؔ਺

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෭࡞༻͕ͳ͍ͱɺԿ͕خ͍͠ͷʁ

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ؔ਺ܕϓϩάϥϛϯάͱ͸ ࠶ w ෭࡞༻͕ͳ͍͜ͱ w ݱࡏͷؔ਺ͷ֎ʹଘࡏ͢ΔσʔλʹཔΒͣ ɺ  ݱࡏͷؔ਺ͷ֎ʹଘࡏ͢ΔσʔλΛมߋ͠ͳ͍

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ࢀরಁաੑ w ಉ͡Ҿ਺Λ༩͑Ε͹ɺඞͣಉ݁͡Ռ͕ฦΔ w ଞͷ͍͔ͳΔػೳͷ݁ՌʹӨڹΛ༩͑ͳ͍

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ࢀরಁաੑ w ಉ͡Ҿ਺Λ༩͑Ε͹ɺඞͣಉ݁͡Ռ͕ฦΔ w ଞͷ͍͔ͳΔػೳͷ݁ՌʹӨڹΛ༩͑ͳ͍ ˠ ෭࡞༻͕ͳ͍˺ࢀরಁաੑ͕ߴ͍

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ࢀরಁաੑ͕ߴ͍ͱ w ॲཧͷཧղͷ͠΍͢͞ w ෭࡞༻ʹΑΔόάΛੜΈͮΒ͍ w ςετ΍อक͕͠΍͍͢

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෭࡞༻͕ͳ͍͜ͱͷσϝϦοτ w ঢ়ଶΛ࣋ͭॲཧΛهड़ͮ͠Β͍ w ྫ͑͹ɺಈըͷϩʔυதɺ࠶ੜதɺఀࢭதͳͲ

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8JO5JDLFU"OESPJEʹ͓͚Δ ؔ਺ܕϓϩάϥϛϯά

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w ࿮൪ɺं൪ w બख৘ใ ࢯ໊ɺ෎ݝɺڃ൝ͳͲ w લճग़৔ͨ͠Ϩʔεͷ੒੷ w ։࠵৔ॴ w άϨʔυ w ֤Ϩʔεͷ݁Ռ ग़૸දલ৔ॴ

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w ࿮൪ɺं൪ w બख৘ใ ࢯ໊ɺ෎ݝɺڃ൝ͳͲ w લճग़৔ͨ͠Ϩʔεͷ੒੷ w ։࠵৔ॴ w άϨʔυ w ֤Ϩʔεͷ݁Ռ ग़૸දલ৔ॴ

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w બख৘ใϦετ w બख*% લճग़৔ͨ͠Ϩʔεͷ*% લ ճग़৔ͨ͠Ϩʔεͷ݁ՌϦετ w ϨʔεΧοϓϦετ w ϨʔεΧοϓ*% ϨʔεΧοϓ໊শ άϨʔυ ڝྠ৔*% w ڝྠ৔Ϧετ w ڝྠ৔*% ڝྠ৔໊শ αʔό͔Β໯͏σʔλ

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var response: KeirinRaceResponse? = null var entries = mutableListOf() fun parse() { for (record in response!!.recordsList) { var previousCup: KeirinCup? = null for (cup in response!!.cupsList) { if (cup.id == record.previousCupId) { previousCup = cup .. αʔό͔Β໯ͬͨσʔλΛύʔε͢Δ

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fun parse(response: KeirinRaceResponse): List { val entries = mutableListOf() for (record in response.recordsList) { var previousCup: KeirinCup? = null for (cup in response.cupsList) { if (cup.id == record.previousCupId) { previousCup = cup break } .. ؔ਺ͷ֎΁ͷ෭࡞༻Λͳ͘͢

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fun parse(response: KeirinRaceResponse): List { val entries = mutableListOf() for (record in response.recordsList) { val previousCup: KeirinCup = response.cupsList.first { it.id == record.previousCupId } val cupVenue: KeirinVenue = response.venuesList.first { it.id == previousCup.venueId } .. entries.add(EntryTable(record, previousCup, cupVenue)) GPSϒϩοΫͷ֎΁ͷ෭࡞༻Λͳ͘͢

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fun parse(response: KeirinRaceResponse): List { return response.recordsList.map { record -> val previousCup: KeirinCup = response.cupsList.first { it.id == record.previousCupId } val cupVenue: KeirinVenue = response.venuesList.first { it.id == previousCup.venueId } .. EntryTable(record, previousCup, cupVenue) GPSϒϩοΫͷ֎΁ͷ෭࡞༻Λͳ͘͢

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"SSPX w ܕ෇͖ؔ਺ܕݴޠΛ࣮ݱ͢ΔͨΊͷ,PUMJO޲͚ϥΠϒϥϦ w "SSPX5SZ w ྫ֎͕ൃੜ͢ΔՄೳੑͷ͋Δؔ਺ͷݺͼग़͠Λ  ϞσϧԽ͢Δ <+1>'VODUJPOBM1SPHSBNNJOHJO,PUMJOXJUI"SSPX IUUQTTQFBLFSEFDLDPNXBTBCFFGKQGVODUJPOBMQSPHSBNNJOHJOLPUMJOXJUIBSSPX

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sealed class Try : TryOf { data class Failure(val exception: Throwable) : Try() data class Success(val value: A) : Try () inline operator fun invoke(f: () -> A): Try = try { Success(f()) } catch (e: Throwable) { Failure(e) } "SSPX5SZ

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val tried = Try { .. } if (tried.isFailure()) { .. } if (tried.isSuccess()) { .. } tried.fold( ifFailure = { .. }, ifSuccess = { .. } ) "SSPX5SZͷγϯϓϧͳ࢖͍ํ

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val tried = Try { .. } if (tried.isFailure()) { .. } if (tried.isSuccess()) { .. } tried.fold( ifFailure = { .. }, ifSuccess = { .. } ) "SSPX5SZͷγϯϓϧͳ࢖͍ํ 5SZ\^ϒϩοΫ಺Ͱ ྫ֎͕ൃੜ͢ΔՄೳੑͷ͋ΔॲཧΛߦ͏

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val tried = Try { .. } if (tried.isFailure()) { .. } if (tried.isSuccess()) { .. } tried.fold( ifFailure = { .. }, ifSuccess = { .. } ) "SSPX5SZͷγϯϓϧͳ࢖͍ํ ྫ֎͕ൃੜͨ͠৔߹ͷॲཧ

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val tried = Try { .. } if (tried.isFailure()) { .. } if (tried.isSuccess()) { .. } tried.fold( ifFailure = { .. }, ifSuccess = { .. } ) "SSPX5SZͷγϯϓϧͳ࢖͍ํ ॲཧ͕੒ޭͨ͠৔߹ͷॲཧ

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val tried = Try { .. } if (tried.isFailure()) { .. } if (tried.isSuccess()) { .. } tried.fold( ifFailure = { .. }, ifSuccess = { .. } ) "SSPX5SZͷγϯϓϧͳ࢖͍ํ GPMEͰ·ͱΊͯهड़͢Δ͜ͱ΋Ͱ͖Δ

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fun parse(response: KeirinRaceResponse): Try> { return Try { response.recordsList.map { record -> val previousCup: KeirinCup = response.cupsList.first { it.id == record.previousCupId } val cupVenue: KeirinVenue = response.venuesList.first { it.id == previousCup.venueId } .. EntryTable(record, previousCup, cupVenue) ॲཧͷࣦഊΛ໭Γ஋Ͱදݱ͢Δ

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w ࿮൪ɺं൪ w બख৘ใ ࢯ໊ɺ෎ݝɺڃ൝ͳͲ w લճग़৔ͨ͠Ϩʔεͷ੒੷ w ։࠵৔ॴ w άϨʔυ w ֤Ϩʔεͷ݁Ռ ग़૸දલ৔ॴ

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·ͱΊ w 8JO5JDLFU"OESPJEΞϓϦ͸ɺཧղ͠΍͘͢ɾ҆શͰɾςε τ͠΍͍͢ίʔυΛॻͨ͘Ίʹɺؔ਺ܕϓϩάϥϛϯάͷཁ ૉΛऔΓೖΕ͍ͯ·͢ w ޲͖ෆ޲͖͕͋ΔͷͰɺ༻๏༻ྔΛकͬͯਖ਼͘͠࢖͍·͠ΐ ͏

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