testing for quiet not a number (QNAN)

[Dylan]

I need to write logic that checks a variable (a float) and branches
when that variable is set to the representation of QNAN.

I thought the following would work, but it doesn't.

if (MyVariable == std::numeric_limits<float>::quiet_NaN())
{
//blah blah
}

Any ideas?

 

[Dylan]

I need to write logic that checks a variable (a float) and branches
when that variable is set to the representation of QNAN.

I thought the following would work, but it doesn't.

if (MyVariable == std::numeric_limits<float>::quiet_NaN())
{
//blah blah
}

Any ideas?

ah ha!

It's okay I found the answer. A NAN will test unequal to any value
even itself, so...

if (MyVariable != MyVariable)
{
//blah blah
}

works

 

[Darius.Moos AT esigma-systems DOT de]

ah ha!
It's okay I found the answer. A NAN will test unequal to any value even
itself, so...
if (MyVariable != MyVariable)
{
//blah blah
}

Don't do that!

man finite
man isnan
man isinf
less /usr/include/math.h: fpclassify, isfinite
http://www.delorie.com/gnu/docs/glibc/libc.html#SEC_Top:
chapter. 20

HTH, Darius.

 

[Richard Herring]

Don't do that!

man finite

The name specified is not recognized as an
internal or external command, operable program or batch file.

man isnan

The name specified is not recognized as an
internal or external command, operable program or batch file.

man isinf

The name specified is not recognized as an
internal or external command, operable program or batch file.

less /usr/include/math.h: fpclassify, isfinite

The name specified is not recognized as an
internal or external command, operable program or batch file.

http://www.delorie.com/gnu/docs/glibc/libc.html#SEC_Top:
chapter. 20

"The GNU C Library"

Can you explain your point by reference to the C++ standard?

 

[Darius.Moos AT esigma-systems DOT de]

[...]
Can you explain your point by reference to the C++ standard?

No ?