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

Transcript

1. %FDJNBMɺਖ਼͘͠࢖ͬͯΔʁ
   forJ1IPOF%FW4BQQPSPGFBU)","5"TXJGU
   

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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 {
   

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3. ʲ଎ใʳΏΊΈɺ҉߸௨՟Λൃߦʂ
   ˞ӕͰ͢ɻ
   

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4. ͱ͍͏Θ͚Ͱ
   

   ΏΊΈͷڅ༩͸:VNF$PJOͰࢧڅʹ
   ˞ӕͰ͢ɻ
   

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5. // ࠓ݄ͷڅ༩
   
   
   var myYumeCoin = 0.2
   
   
   // ࠓ݄ͷϘʔφε
   
   
   myYumeCoin += 0.1
   
   
   // ϘʔφεΛ࢖ͬͯങ͍෺ʂ
   
   
   myYumeCoin -= 0.1
   
   
   // ࢒ߴ֬ೝ
   
   
   print(myYumeCoin) // 0.20000000000000004 ??????
   

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

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7. Decimal
   

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

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9. // ࠓ݄ͷڅ༩
   
   
   var myYumeCoin = 0.2
   
   
   // ࠓ݄ͷϘʔφε
   
   
   myYumeCoin += 0.1
   
   
   // ϘʔφεΛ࢖ͬͯങ͍෺ʂ
   
   
   myYumeCoin -= 0.1
   
   
   // ࢒ߴ֬ೝ
   
   
   print(myYumeCoin) // 0.20000000000000004 ??????
   

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10. import Foundation
    
    
    // ࠓ݄ͷڅ༩
    
    
    var myYumeCoin: Decimal = 0.2
    
    
    // ࠓ݄ͷϘʔφε
    
    
    myYumeCoin += 0.1
    
    
    // ϘʔφεΛ࢖ͬͯങ͍෺ʂ
    
    
    myYumeCoin -= 0.1
    
    
    // ࢒ߴ֬ೝ
    
    
    print(myYumeCoin) // 0.2 🎉
    'PVOEBUJPO͕ඞཁ
    ܕΛ໌ࣔతʹ%FDJNBMʹࢦఆ
    

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11. DecimalɺŜƃŤƄƃŬžŜŘŢŦ
    

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12. DecimalɺŜƃŤƄƃŬžŜŘŢŦ
    ͱɺࢥͬͨʁ
    

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13. import Foundation
    
    
    // ࠓ݄ͷڅ༩
    
    
    var myYumeCoin: Decimal = 0.2
    
    
    // ࠓ݄ͷϘʔφε
    
    
    myYumeCoin += 0.1
    
    
    // ϘʔφεΛ࢖ͬͯങ͍෺ʂ
    
    
    myYumeCoin -= 0.1
    
    
    // ࢒ߴ֬ೝ
    
    
    print(myYumeCoin) // 0.2 🎉
    

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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 !!!?????
    

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15. DecimalɺūŬŹƂŜŽūŘ
    

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16. DecimalͷϦςϥϧ୅ೖ
    w খ਺ϦςϥϧͰDecimalΛ୅ೖͰ͖Δͷ͸ɺ
    ExpressibleByFloatLiteralΛར༻ͨ݁͠Ռ
    w ࣮૷͸init(floatLiteral value: Double)
    w DecimalΛ࡞Δલʹͦ΋ͦ΋ઌʹҰճDoubleΛ
    ࡞ͬͯͦͷ݁ՌΛ୅ೖ͍ͯ͠Δ͚ͩʂ
    

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17. খ਺ϦςϥϧͰ
    

    DecimalΛ୅ೖ͠ͳ͍Ͱʂ
    

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18. %FDJNBMΛखܰʢʁʣʹѻ͏ͨΊͷ
    

    ΠχγϟϥΠβʔ
    • init(_ value: String, format: Decimal.FormatStyle,
    lenient: Bool = true) throws // iOS 15+
    
    
    • init?(string: String, locale: Locale? = nil) // iOS 7+
    
    
    • // etc…
    

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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 !!!?????
    

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20. import Foundation
    
    
    // …
    
    
    // Decimal Λ࢖ͬͯਖ਼֬ͳڅ༩ܭࢉ͕Ͱ͖͔ͨΒ͍͑΍Ϙʔφεʂ
    
    
    //myYumeCoin += 123.456
    
    
    // ࠓ౓ͦ͜ʂ
    
    
    myYumeCoin += try! .init("123.456", format: .number)
    
    
    // ࢒ߴ֬ೝ
    
    
    print(myYumeCoin) // 123.656 🎉
    

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21. DecimalɺͪΐͬͱͰ͖͔ͨͳ
    

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22. ʲࢀߟʳ
    

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23. IUUQTGPSVNTTXJGUPSHUIPXUPJOJUJBMJ[FEFDJNBM
    

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24. IUUQTJEFBMSFBMJUZDPNQSPHSBNJOHTXJGUEFDJNBMTUSJOH
    

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25. ʲએ఻ʳ
    

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26. IUUQTZVNFNJDPOOQBTTDPNFWFOU
    

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27. IUUQTXXXZVNFNJDPKQDBUFHPSZSFDSVJU
    

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