这三个特殊的浮点值是什么意思：正无穷大，负无穷大，NaN？ [英] What do these three special floating-point values mean: positive infinity, negative infinity, NaN?

问题描述

我们如何在代码中使用它们，会导致NaN（不是数字）？ href =http://introcs.cs.princeton.edu/java/91float/ =nofollow noreferrer>如果你想了解更多关于Java中的浮点数的信息，这可能是一个很好的参考。

正无穷大是一个很大的正数，不能正常表示。负无限是一个负数，如此大以至于无法正常表示。 NaN的意思是不是一个数字，它是一个数学运算的结果，它不产生类似数字0的数字。在Java中，Double和Float类都有常数来代表所有三种情况。他们是POSITIVE_INFINITY，NEGATIVE_INFINITY和NaN。

另外考虑这个：

pre $ double a = Math.pow（10，600） - Math.pow（10，600）; // == NaN


在数学上，每个人都可以看到它是0.但是对于机器来说，一个Infinity - Infinity（相同的Rank），这确实是NaN。

How can we use them in our codes, and what will cause NaN(not a number)?

解决方案

This may be a good reference if you want to learn more about floating point numbers in Java.

Positive Infinity is a positive number so large that it can't be represented normally. Negative Infinity is a negative number so large that it cannot be represented normally. NaN means "Not a Number" and results from a mathematical operation that doesn't yield a number- like dividing 0 by 0.

In Java, the Double and Float classes both have constants to represent all three cases. They are POSITIVE_INFINITY, NEGATIVE_INFINITY, and NaN.

Plus consider this:

double a = Math.pow(10, 600) - Math.pow(10, 600); //==NaN

Mathematically, everybody can see it is 0. But for the machine, it is an "Infinity" - "Infinity" (of same Rank), which is indeed NaN.

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