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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

_isnan

Checks a given double-precision floating-point value for not a number (NAN).

int _isnan( 
   double x  
);

x

Double-precision floating-point value.

_isnan returns a nonzero value if the argument x is a NAN; otherwise it returns 0.

The _isnan function tests a given double-precision floating-point value x, returning a nonzero value if x is a not a number (NAN). A NAN is generated when the result of a floating-point operation cannot be represented in Institute of Electrical and Electronics Engineers (IEEE) format. For information about how a NAN is represented for output, see printf.

Routine

Required header

_isnan

<float.h>

For more compatibility information, see Compatibility in the Introduction.

Libraries

All versions of the C run-time libraries.

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