Lua检查数字/值是否为nan [英] Lua check if a number/value is nan

问题描述

我编写了一个程序，在经过一些计算后打印出矩阵，我得到了所有元素的nan输出.我想在矩阵的第一个元素变为nan后立即中断for循环，以了解该问题.我怎样才能做到这一点?在终端中，我打印了包含nan作为所有元素的矩阵a，并分别键入了a[1][1]=="nan"和a[{{1},{1}}]=="nan"，这两个均返回false.他们为什么不返回false，我应该改用什么语句?

I have written a program to print a matrix after some computations and I am getting an output of nan for all elements. I want to break a for loop as soon as the matrix's first element becomes nan to understand the problem. How can I do this? In the terminal, I have printed the matrix a containing nan as all elements and typed a[1][1]=="nan" and a[{{1},{1}}]=="nan" both of which return false. Why are they not returning false and what statement should I use instead?

推荐答案

您的测试失败，因为您正在将数字与字符串"nan"进行比较.

Your test fails because you are comparing a number with a string, "nan".

如果确定是数字，最简单的方法是:

If you are sure it's a number, the easiest way is:

if a[1][1] ~= a[1][1] then

因为根据IEEE 754，nan值被认为不等于任何值，包括其自身.

because according to IEEE 754, a nan value is considered not equal to any value, including itself.

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