如何在Swift中找到Double和Float的最大值

Current learning Swift, there are ways to find max and min value for different kind of Integer like Int.max and Int.min.

现有的快速学习算法，对于不同类型的整数，如Int.max和Int.min，都有求最大值和最小值的方法。

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.

有没有一种方法可以找到Double和Float的最大值?另外，这类问题我应该参考哪一份文件?我目前正在阅读苹果的Swift编程语言。

4 个解决方案

#1

While there’s no Double.max, it is defined in the C float.h header, which you can access in Swift via import Darwin.

虽然没有翻倍。max，它是在C浮点数中定义的。h header，你可以通过import Darwin快速访问。

import Darwin

let fmax = FLT_MAX
let dmax = DBL_MAX

These are roughly 3.4 * 10^38 and 1.79 * 10^308 respectively.

这些是约3.4 * 10 ^ 38岁,分别为1.79 * 10 ^ 308。

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:

但请记住，浮点数并不简单(浮点数也不简单)。当保持这么大的数字时，您将以类似于在非常小的数字中失去精度的方式失去精度，因此:

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.

在你开始计算这些极限之前，你应该先读一下浮点数。这里和这里可能是一个好的开始。

#2

As of Swift 3, you should use:

在Swift 3中，您应该使用:

CGFloat.greatestFiniteMagnitude
Double.greatestFiniteMagnitude
Float.greatestFiniteMagnitude

#3

AV's answer is fine, but I find those macros hard to remember and a bit non-obvious, so eventually I made Double.MIN and friends work:

AV的答案是好的，但是我发现这些宏很难记住，而且有点不明显，所以最终我做了Double。最小值和朋友工作:

extension Double {
    static var MIN     = -DBL_MAX
    static var MAX_NEG = -DBL_MIN
    static var MIN_POS =  DBL_MIN
    static var MAX     =  DBL_MAX
}

Don't use lowercase min and max -- those symbols are used in Swift 3.

不要使用小写的最小值和最大值——这些符号在Swift 3中使用。

#4

Just Write

只写

    let mxFloat = MAXFLOAT

You will get maximum value of float in swif.

您将在swif中获得浮点数的最大值。

#1