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Name

isnan - test for a NaN

Synopsis

#include <math.h>

int isnan(real-floating x);

Description

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.

The isnan() macro shall determine whether its argument value is a NaN. First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.

Return Value

The isnan() macro shall return a non-zero value if and only if its argument has a NaN value.

Errors

No errors are defined.

The following sections are informative.

Examples

None.

Application Usage

None.

Rationale

None.

Future Directions

None.

See Also

fpclassify() , isfinite() , isinf() , isnormal() , signbit() , the Base Definitions volume of IEEE Std 1003.1-2001, <math.h>

Copyright

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

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