如何在Swift 3中使用帶浮點值的sin（_：）

Question

import Foundation 
public func sine <T: FloatingPoint > (_ x: T ) -> T{ 
    return sin(x) 
} 
// Error: Cannot invoke 'sin' with an argument list of type '(T)' 

有沒有辦法解決這個問題？ 非常感謝。

Answer 1

你可以說，也接受浮點類型如下贖罪方法：

import UIKit 

func sin<T: FloatingPoint>(_ x: T) -> T { 
    switch x { 
    case let x as Double: 
     return sin(x) as? T ?? 0 
    case let x as CGFloat: 
     return sin(x) as? T ?? 0 
    case let x as Float: 
     return sin(x) as? T ?? 0 
    default: 
     return 0 as T 
    } 
} 

另一種選擇是添加一個方法或計算的屬性擴展到浮點類型如下：

extension FloatingPoint { 
    var sin: Self { 
     switch self { 
     case let x as Double: 
      return UIKit.sin(x) as? Self ?? 0 
     case let x as CGFloat: 
      return UIKit.sin(x) as? Self ?? 0 
     case let x as Float: 
      return UIKit.sin(x) as? Self ?? 0 
     default: 
      return 0 as Self 
     } 
    } 
}