Decimal、正しく使ってる？ / Are you using Decimal correctly?

Transcript

1. %FDJNBMɺਖ਼͘͠࢖ͬͯΔʁ for
   J1IPOF
   %FW
   4BQQPSP
   GFBU
   )","5"TXJGU

2. } var employedBy = "YUMEMI Inc." var job = "iOS

   Tech Lead" var favoriteLanguage = "Swift" var twitter = "@lovee" var qiita = "lovee" var github = "el-hoshino" var additionalInfo = """ M1 Max MacBook Proࠓ೔ಧ͍ͨʂ """ final class Me: Developable, Talkable {

3. ʲ଎ใʳΏΊΈɺ҉߸௨՟Λൃߦʂ ˞ӕͰ͢ɻ

4. ͱ͍͏Θ͚Ͱ 
 ΏΊΈͷڅ༩͸
   :VNF$PJO
   Ͱࢧڅʹ ˞ӕͰ͢ɻ

5. // ࠓ݄ͷڅ༩ var myYumeCoin = 0.2 // ࠓ݄ͷϘʔφε myYumeCoin +=

   0.1 // ϘʔφεΛ࢖ͬͯങ͍෺ʂ myYumeCoin -= 0.1 // ࢒ߴ֬ೝ print(myYumeCoin) // 0.20000000000000004 ??????

6. ͳͥ͜Μͳ͜ͱ͕ى͜Δͷ͔ w 4XJGU
   Ͱখ਺Λѻ͏ͱ͖ɺσϑΥϧτͰ͸
   Double
   ͕ ࢖ΘΕΔ
   w Double
   ͸ʮഒਫ਼౓ුಈখ਺఺਺ʯͳͷͰɺਫ਼౓ͷ໰ ୊Ͱͦ΋ͦ΋ਖ਼֬ʹදͤͳ͍਺ࣈ͕ͨ͘͞Μ͋Δ
   w େ఍ͷ৔߹͸ͦͷؙΊΒΕͨ਺ࣈͰ΋໰୊ʹͳΒͳ͍ ͕ɺۚ༥ܥͳͲͷ৔߹͸ਖ਼֬ʹѻ͏ඞཁ͕͋Δ

7. Decimal

8. Decimal
   ܕ w ුಈখ਺఺਺Λेਐ਺ϕʔεͰѻ͏ͨΊͷܕ
   w ༗ޮܻ਺͕
   
   ܻ
   w ༗ޮܻ਺ൣғ಺Ͱ͋Ε͹ेਐ਺දهͷޡ͕ࠩͳ͍

9. // ࠓ݄ͷڅ༩ var myYumeCoin = 0.2 // ࠓ݄ͷϘʔφε myYumeCoin +=

   0.1 // ϘʔφεΛ࢖ͬͯങ͍෺ʂ myYumeCoin -= 0.1 // ࢒ߴ֬ೝ print(myYumeCoin) // 0.20000000000000004 ??????

10. import Foundation // ࠓ݄ͷڅ༩ var myYumeCoin: Decimal = 0.2 //

    ࠓ݄ͷϘʔφε myYumeCoin += 0.1 // ϘʔφεΛ࢖ͬͯങ͍෺ʂ myYumeCoin -= 0.1 // ࢒ߴ֬ೝ print(myYumeCoin) // 0.2 🎉 'PVOEBUJPO
    ͕ඞཁ ܕΛ໌ࣔతʹ
    %FDJNBM
    ʹࢦఆ

11. DecimalɺŜƃŤƄƃŬžŜŘŢŦ

12. DecimalɺŜƃŤƄƃŬžŜŘŢŦ
    ͱɺࢥͬͨʁ

13. import Foundation // ࠓ݄ͷڅ༩ var myYumeCoin: Decimal = 0.2 //

    ࠓ݄ͷϘʔφε myYumeCoin += 0.1 // ϘʔφεΛ࢖ͬͯങ͍෺ʂ myYumeCoin -= 0.1 // ࢒ߴ֬ೝ print(myYumeCoin) // 0.2 🎉

14. import Foundation // ࠓ݄ͷڅ༩ var myYumeCoin: Decimal = 0.2 //

    ࠓ݄ͷϘʔφε myYumeCoin += 0.1 // ϘʔφεΛ࢖ͬͯങ͍෺ʂ myYumeCoin -= 0.1 // Decimal Λ࢖ͬͯਖ਼֬ͳڅ༩ܭࢉ͕Ͱ͖͔ͨΒ͍͑΍Ϙʔφεʂ myYumeCoin += 123.456 // ࢒ߴ֬ೝ print(myYumeCoin) // 123.65599999999997952 !!!?????

15. DecimalɺūŬŹƂŜŽūŘ

16. Decimal
    ͷϦςϥϧ୅ೖ w খ਺ϦςϥϧͰ
    Decimal
    Λ୅ೖͰ͖Δͷ͸ɺ
    ExpressibleByFloatLiteral
    Λར༻ͨ݁͠Ռ
    w ࣮૷͸
    init(floatLiteral value: Double)
    w Decimal
    Λ࡞Δલʹͦ΋ͦ΋ઌʹҰճ
    Double
    Λ

    ࡞ͬͯͦͷ݁ՌΛ୅ೖ͍ͯ͠Δ͚ͩʂ

17. খ਺ϦςϥϧͰ 
 Decimal
    Λ୅ೖ͠ͳ͍Ͱʂ

18. %FDJNBM
    Λखܰʢʁʣʹѻ͏ͨΊͷ 
 ΠχγϟϥΠβʔ • init(_ value: String, format: Decimal.FormatStyle, lenient:

    Bool = true) throws // iOS 15+ • init?(string: String, locale: Locale? = nil) // iOS 7+ • // etc…

19. import Foundation // ࠓ݄ͷڅ༩ var myYumeCoin: Decimal = 0.2 //

    ࠓ݄ͷϘʔφε myYumeCoin += 0.1 // ϘʔφεΛ࢖ͬͯങ͍෺ʂ myYumeCoin -= 0.1 // Decimal Λ࢖ͬͯਖ਼֬ͳڅ༩ܭࢉ͕Ͱ͖͔ͨΒ͍͑΍Ϙʔφεʂ myYumeCoin += 123.456 // ࢒ߴ֬ೝ print(myYumeCoin) // 123.65599999999997952 !!!?????

20. import Foundation // … // Decimal Λ࢖ͬͯਖ਼֬ͳڅ༩ܭࢉ͕Ͱ͖͔ͨΒ͍͑΍Ϙʔφεʂ //myYumeCoin += 123.456

    // ࠓ౓ͦ͜ʂ myYumeCoin += try! .init("123.456", format: .number) // ࢒ߴ֬ೝ print(myYumeCoin) // 123.656 🎉

21. DecimalɺͪΐͬͱͰ͖͔ͨͳ

22. ʲࢀߟʳ

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25. ʲએ఻ʳ

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