测试 Float 值是否为 NaN
可能的重复：
检查双精度数（或浮点数）是否为C++ 中的 nan
我需要检查 float 是否为 NaN。通过浏览一些链接，我找到了最常见的检查。
FLOAT32 f32_test_NaN = (some_value);
if (f32_test_NaN == f32_test_NaN)
{
//do something;
}
else
{
// do something;
}
但这似乎对我不起作用。我的代码如下：
FLOAT32 test_NaN = 0x414570A3;//some value - is this ok?
在GDB上调试：
(gdb) p test_NaN
$1 = 1.09506982e+09
(gdb) p/x test_NaN
$2 = 0x41457080 // Hex is not same as init value - What is compiler doing?
所以在我的例子中，test_NaN等于test_NaN。
如果需要进行任何编译器设置，请告诉我。我在Solaris 上运行。或者有没有其他方法可以检查相同的情况。
提前致谢。
Possible Duplicate:
Checking if a double (or float) isnanin C++
I have a requirement to check if float is NaN. By going through some of the links I found the most common check.
FLOAT32 f32_test_NaN = (some_value);
if (f32_test_NaN == f32_test_NaN)
{
//do something;
}
else
{
// do something;
}
But this does not seem to work for me. My code is as follows:
FLOAT32 test_NaN = 0x414570A3;//some value - is this ok?
Debugging on GDB:
(gdb) p test_NaN
$1 = 1.09506982e+09
(gdb) p/x test_NaN
$2 = 0x41457080 // Hex is not same as init value - What is compiler doing?
So in my case test_NaN is equal to test_NaN.
Please let me know if any compiler setting has to be done. I am running on solaris. Or is there any other way to check the same.
Thanks in advance.
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包含
math.h并使用int isnan(x)。不要忘记使用-lm链接Include
math.hand useint isnan(x). Don't forget to link with-lm如果
If
<math.h>is not available, then do this:if (x != x)
对于 x = 0x7FBFFFFF（符号位 0，a = 0，其余位 1）
http://en.wikipedia.org/wiki/NaN
if (x != x)
For x = 0x7FBFFFFF (sign bit 0, a = 0, rest of bits 1)
http://en.wikipedia.org/wiki/NaN
问题可能出在您的初始化中（至少解释了您在 gdb 中看到的值）：
给定的十六进制值被视为整数并转换为浮点数（带有指数和值），这意味着它以不同的格式存储。
如果你想强制浮点数内的位，那么你需要 memcpy：
The problem is maybe in your initialization (at least that explains the value you see in gdb) :
The hex value given is considered as an integer and converted to float (with exponent and value) meaning it is stored in a different format.
If you want to force the bits inside the float, then you need to memcpy: