签名检查NaN值 [英] Sign check for NaN value

问题描述

我的程序在计算过程中可以生成nan或-nan值. 我使用isnan方法检查值是否为nan/-nan.

My program during calculation can generate nan or -nan values. I check if the values are nan/-nan using isnan method.

我还必须区分nan值是正还是负(nan或-nan).我该怎么办?

I also have to distinguish if the nan value is positive or negative (nan or -nan). How can I do this?

添加:我需要用于WIN和Unix/Linux的跨平台解决方案

Added:I need crossplatform solution for WIN and for Unix/Linux

推荐答案

从<math.h>尝试signbit:

说明

signbit()是一个通用宏，可以在所有实际浮点上工作 类型.如果x的值具有符号位，则返回非零值 设置.

signbit() is a generic macro which can work on all real floating-point types. It returns a nonzero value if the value of x has its sign bit set.

...

NaN和无穷大都有一个符号位.

它显然是C99和POSIX.1-2001的一部分，但是如果您不想使用/遵循两者中的任何一个，则可以自己编写宏/函数.

It's apparently part of C99 and POSIX.1-2001, but you could write a macro/function yourself if you don't want to use/conform to either of the two.

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