ISNAN(3M) | Mathematical Library Functions | ISNAN(3M) |

isnan - test for NaN

cc [flag... ]file...-lm[library... ] #include <math.h>intisnan(doublex);

c99 [flag... ]file...-lm[library... ] #include <math.h>intisnan(real—floatingx);

In C90 mode, the **isnan()** function tests whether *x* is
NaN.

In C99 mode, the **isnan()** macro determines whether its
argument value is NaN. First, an argument represented in a format wider than
its semantic type is converted to its semantic type. The determination is
then based on the type of the argument.

Both the **isnan()** function and macro return non-zero if and
only if *x* is NaN.

No errors are defined.

In C99 mode, the practice of explicitly supplying a prototype for
**isnan()** after the line

#include <math.h>

is obsolete and will no longer work.

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE | ATTRIBUTE VALUE |

Interface Stability | Standard |

MT-Level | MT-Safe |

math.h(3HEAD), fpclassify(3M), isfinite(3M), isinf(3M), isnormal(3M), signbit(3M), attributes(7), standards(7)

July 12, 2006 | SunOS 5.11 |