Objective-C-浮点数检查nan [英] Objective-C - float checking for nan

问题描述

我有一个变量(float slope)，由于有时会被0除，因此在打印时有时会具有nan值.

I have a variable (float slope) that sometimes will have a value of nan when printed out since a division by 0 sometimes happens.

我正在尝试在发生这种情况时进行if-else操作.我怎样才能做到这一点? if (slope == nan)似乎不起作用.

I am trying to do an if-else for when that happens. How can I do that? if (slope == nan) doesn't seem to work.

推荐答案

两种方法，或多或少等效:

Two ways, which are more or less equivalent:

if (slope != slope) {
    // handle nan here
}

或

#include <math.h>
...
if (isnan(slope)) {
    // handle nan here
}

(man isnan将为您提供更多信息，或者您可以在C标准中阅读所有信息)

(man isnan will give you more information, or you can read all about it in the C standard)

或者，您可以在进行除法之前检测到分母为零(或者，如果要在斜率上最终使用atan而不是进行其他一些计算，请使用atan2).

Alternatively, you could detect that the denominator is zero before you do the divide (or use atan2 if you're just going to end up using atan on the slope instead of doing some other computation).

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