为什么-0存在？ [英] Why does -0 exist?

问题描述

尝试使用JavaScript时。我正在测试一些奇怪的小代码片段，这里有一些我的发现（为了帮助我理解我的生活方式 -0 ），

While experimenting with JavaScript. I was testing around with some odd little code snippets, here are a few of my findings (to help understand how I came upon -0),

在控制台中执行 + [] 时，返回 0 。我不确定为什么，但确实如此。
所以，这意味着数组的正数是 0 ..

While doing +[] in console, this returns 0. I'm not sure why, but it does. So, this implies the positive of a array is 0..

这样做后，我好奇并尝试了以下内容：

After doing so, I got curious and tried the following:

console.log(-[]);

这会返回 -0 ...

-0是什么意思？ 0和-0都没有值，所以负面实际上是不必要的......或者是它？也许JavaScript的目的是-0？

What is the point of -0? 0 and -0 both hold no value, so the negative is really unnecessary... Or is it? Perhaps JavaScript has a purpose for -0?

添加到它上面。除了使用 -0 本身或使用 -0 > - [] ...

Adding onto that. I cannot find any other way to reproduce -0 other than using -0 itself, or using -[]...

其他一些奇怪的发现，继续我的问题 -0

Some other weird findings, furthing my question of -0

(-0) + (-0) = 0
(-0) - (-0) = -0
(-0) * (-0) = 0
(-0) / (-0) = NaN // of course

推荐答案

JavaScript使用 IEEE 754标准代表数字。来自维基百科：

JavaScript uses IEEE 754 standard to represent numbers. From Wikipedia:

有符号零为零且带有相关符号。在普通算术中，-0 = + 0 = 0.但是，在计算中，某些数字表示允许存在两个零，通常用 -0（负零）和 +0表示（正零）。这发生在整数的一些有符号数表示中，并且在大多数浮点数表示中。数字0通常编码为+0，但可以用+0或-0表示。

Signed zero is zero with an associated sign. In ordinary arithmetic, −0 = +0 = 0. However, in computing, some number representations allow for the existence of two zeros, often denoted by −0 (negative zero) and +0 (positive zero). This occurs in some signed number representations for integers, and in most floating point number representations. The number 0 is usually encoded as +0, but can be represented by either +0 or −0.

用于浮点运算的IEEE 754标准（目前大多数都使用）支持浮点数的计算机和编程语言需要+0和-0。零可以被认为是扩展实数线的变体，使得1 / -0 =-∞和1 / + 0 = +∞，除以0仅对于±0 /±0和±∞/±∞未定义。

The IEEE 754 standard for floating point arithmetic (presently used by most computers and programming languages that support floating point numbers) requires both +0 and −0. The zeroes can be considered as a variant of the extended real number line such that 1/−0 = −∞ and 1/+0 = +∞, division by zero is only undefined for ±0/±0 and ±∞/±∞.

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