如何在Swift中找到Double和Float的最大值 [英] How to find max value for Double and Float in Swift

问题描述

目前正在学习Swift，有一些方法可以找到不同类型的整数的 max 和 值，如 Int .max 和 Int.min 。

有没有办法找到Double和Float的最大值？此外，我应该提及哪个文件提出这样的问题？我正在阅读Apple的 Swift编程语言。

解决方案

虽然没有 Double.max ，它定义在C float.h 标题中，您可以通过导入在Swift中访问达尔文。

  import达尔文
 
 let fmax = FLT_MAX 
 let dmax = DBL_MAX 
  

这些大概是 3.4 * 10 ^ 38 和 1.79 * 10 ^ 308

但是请记住，它不是那么简单浮点数（浮点数并不简单）。当你拿着这个数字很大的时候，你会以类似的方式失去精确度，以非常小的数字丢失精度，所以：

  let d = DBL_MAX 
 let e = d  -  1.0 
 let diff = d  -  e 
 diff == 0.0 // true 
 
 let maxPlusOne = DBL_MAX + 1 
 maxPlusOne == d // true 
 
 let inf = DBL_MAX * 2 
 //也许无穷大是最大
 inf == Double.infinity // true $ b $因此，在进行一些可能会刷新这些限制的计算之前，您应该可以读取浮点数。 此处和 here 可能是一个好的开始。
 
Current learning Swift, there are ways to find max and min value for different kind of Integer like Int.max and Int.min. 

Is there a way to find max value for Double and Float? Moreover, which document should I refer for this kind of question? I am currently reading Apple's The Swift Programming Language.
解决方案
While there’s no Double.max, it is defined in the C float.h header, which you can access in Swift via import Darwin.
import Darwin

let fmax = FLT_MAX
let dmax = DBL_MAX
These are roughly 3.4 * 10^38 and 1.79 * 10^308 respectively.

But bear in mind it’s not so simple with floating point numbers (it’s never simple with floating point numbers). When holding numbers this large, you lose precision in a similar way to losing precision with very small numbers, so:
let d = DBL_MAX
let e = d - 1.0
let diff = d - e
diff == 0.0  // true

let maxPlusOne = DBL_MAX + 1
maxPlusOne == d  // true

let inf = DBL_MAX * 2
// perhaps infinity is the "maximum" 
inf == Double.infinity  // true
So before you get into some calculations that might possibly brush up against these limits, you should probably read up on floating point.  Here and here are probably a good start.

                        
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