Kotlin/Swift 有理数クラスのすすめ

Kotlin/Swift 有理数クラスのすすめ

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Koichiro Oishi

August 10, 2017
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  1. 10.

    Ϋϥεͷఆٛ(Kotlin) ෼ࢠͱ෼฼ΛϓϩύςΟͱͯ࣋ͭ͠ΫϥεRational Λఆٛ͢Δ class Rational(val numerator: Int, val denominator: Int)

    • numeratorͱdenominator͸͜Ε͚ͩͰϓϩύςΟ ʹͳΔɻ • ͪͳΈʹval͸ఆ਺ɺvar͸ม਺ 10 Koichiro Oishi, 2017/08/08
  2. 11.

    Ϋϥεͷఆٛ(Swift) struct Rational { let numerator: Int let denominator: Int

    } let rational = Rational(numerator: 1, denominator: 2) • ϓϩύςΟΛఆٛ͢Ε͹ΠχγϟϥΠβͷҾ਺ͱ ͯͦ͠ͷ··࢖͑Δ • ͪͳΈʹlet͸ఆ਺ɺvar͸ม਺ 11 Koichiro Oishi, 2017/08/08
  3. 12.

    ϝιουͷఆٛ(Kotlin) print(rational)ͨ͠ࡍʹ஋ͷදࣔΛͰ͖ΔΑ͏ʹ͢Δ Rational@279f2327 Ͱ͸ͳ͘ 1/2 ͳͲͱ͍ͨ͠ class Rational(val numerator: Int,

    val denominator: Int) { override fun toString(): String = "${numerator}/${denominator}" } • toString()ΛΦʔόϥΠυ͢Δ 12 Koichiro Oishi, 2017/08/08
  4. 13.

    ϝιουͷఆٛ(Swift) extension Rational: CustomStringConvertible { var description: String { return

    "\(numerator)/\(denominator)" } } • CustomStringConvertibleϓϩτίϧʹ४ڌͨ͠ extensionͰdescriptionϓϩύςΟΛ࣮૷ 13 Koichiro Oishi, 2017/08/08
  5. 14.

    ΠχγϟϥΠβ(Kotlin) ෼฼ʹ0͕୅ೖ͞Εͨ৔߹͸Τϥʔͱ͢ΔͨΊΠχ γϟϥΠβͰ࣮૷͢Δ class Rational(val numerator: Int, val denominator: Int)

    { init { require(denominator != 0, {"denominator must not be null"}) } override fun toString(): String = "${numerator}/${denominator}" } • ؔ਺requireͰ෼฼͕0Ҏ֎Ͱ͋Δ͜ͱΛཁٻɺ൓ ͨ͠৔߹͸ΤϥʔΛ౤͛Δ 14 Koichiro Oishi, 2017/08/08
  6. 15.

    ΠχγϟϥΠβ(Swift ͦͷ1) ࣦഊͨ͠Βྫ֎Λ౤͛Δύλʔϯ init(numerator: Int, denominator: Int) throws { if

    denominator == 0 { throw NSError(domain: "denominator must not be null", code: -1, userInfo: nil) } self.numerator = numerator self.denominator = denominator } • ࠓճ͸ͪ͜ΒΛྫͰਐΊ·͢ 15 Koichiro Oishi, 2017/08/08
  7. 16.

    ΠχγϟϥΠβ(Swift ͦͷ2) ࣦഊͨ͠ΒnilΛฦ͢ύλʔϯ init?(numerator: Int, denominator: Int) { if denominator

    == 0 { return nil } self.numerator = numerator self.denominator = denominator } • ໭Γ஋͕Optionalܕʹ • ݺͼग़͠ଆͰUnwrap͕ඞཁ 16 Koichiro Oishi, 2017/08/08
  8. 17.

    ඇެ։ϓϩύςΟϝιου(Kotlin) ࠷େެ໿਺(greatest common divisor)ΛٻΊ͍ͨ ྫ͑͹ɺ4/6ͷ৔߹͸2/3ͱ͍ͨ͠ɻ tailrec private fun gcd(a: Int,

    b: Int): Int = if (b == 0) a else gcd(b, a% b) • private͚ͭΕ͹ϓϥΠϕʔτ • ͞Βʹ࠶ؼؔ਺ʹ͸tailrecΛ͚ͭΔ 17 Koichiro Oishi, 2017/08/08
  9. 18.

    ඇެ։ϓϩύςΟϝιου(Swift ͦͷ1) ಉ͘͡࠷େެ໿਺(greatest common divisor)ΛٻΊΔ ϝιου private func gcd(a: Int,

    b: Int) -> Int { return b == 0 ? a : gcd(a: b, b: a % b) } • ϩδοΫࣗମ͸ಉ͡ 18 Koichiro Oishi, 2017/08/08
  10. 19.

    ඇެ։ϓϩύςΟϝιου(Swift ͦͷ2) extension Rational: CustomStringConvertible { var description: String {

    let g = gcd(a: abs(numerator), b: abs(denominator)) return "\(numerator/g)/\(denominator/g)" } private func gcd(a: Int, b: Int) -> Int { return b == 0 ? a : gcd(a: b, b: a % b) } } ࣮૷લˠ10/6 ࣮૷ޙˠ5/3 19 Koichiro Oishi, 2017/08/08
  11. 20.

    ԋࢉࢠΦʔόʔϩʔυ(Kotlin ͦͷ1) ϝιουplusΛ௥Ճͯ͠Rationalಉ࢜ͷ଍͠ࢉΛͰ͖ ΔΑ͏ʹ͢Δ fun plus(that: Rational): Rational = Rational(

    numerator * that.denominator + that.numerator * denominator, denominator * that.denominator ) • rational1.plus(rational2) ͱॻ͚ΔΑ͏ʹͳΔ 20 Koichiro Oishi, 2017/08/08
  12. 21.

    ԋࢉࢠΦʔόʔϩʔυ(Kotlin ͦͷ2) ͞Βʹrational1 + ratiolan2 Έ͍ͨʹॻ͖͍ͨ operator fun plus(that: Rational):

    Rational = Rational( numerator * that.denominator + that.numerator * denominator, denominator * that.denominator ) • ԋࢉࢠΦʔόʔϩʔυ = operator overload Rational(10, 6) + Rational(1, 3) 2/1 ͱͰ͖Δ 21 Koichiro Oishi, 2017/08/08
  13. 22.

    ԋࢉࢠΦʔόʔϩʔυ(Swift) SwiftͰԋࢉࢠΛΦʔόʔϩʔυ͢Δͱ͜͏ͳΔ static func +(left: Rational, right: Rational) -> Rational

    { return try! Rational( numerator: left.numerator * right.denominator + right.numerator * left.denominator, denominator: left.denominator * right.denominator) } 22 Koichiro Oishi, 2017/08/08
  14. 23.

    ϝιουͷΦʔόʔϩʔυ(Kotlin) Rational(1, 2) + 1ͷΑ͏ͳܭࢉΛͰ͖ΔΑ͏ʹ͢Δɻ operator fun plus(n: Int): Rational

    = Rational(numerator + n * denominator, denominator) Rational(10, 6) + 1 8/3 ͱͰ͖ΔΑ͏ʹ 23 Koichiro Oishi, 2017/08/08
  15. 24.

    ϝιουͷΦʔόʔϩʔυ(Swift) static func +(rational: Rational, int: Int) -> Rational {

    return try! Rational(numerator: rational.numerator + int * rational.denominator, denominator: rational.denominator) } 24 Koichiro Oishi, 2017/08/08
  16. 26.

    ֦ுؔ਺(Swift) • +ʹҾ਺ͱͯ͠ࠨลInt + ӈลRationalΛ࣮૷ static func +(left: Int, right:

    Rational) -> Rational { return right + left } 26 Koichiro Oishi, 2017/08/08
  17. 27.

    ·ͱΊ ΍ͬͨ͜ͱ • Ϋϥεͷఆٛ • ϓϩύςΟɺϝιουɺΠχγϟϥΠβͷఏࣔ • ؔ਺Φʔόϩʔυ • طଘͷܕʹϝιουΛ௥Ճ(֦ுؔ਺)

    ଞͷݴޠͰ΋༗ཧ਺Ϋϥεͷ࣮૷Λͯ͠ΈΔͱษڧʹͳ Γͦ͏Ͱ͢Ͷʁ 27 Koichiro Oishi, 2017/08/08