NAME

       isnan - test for a NaN

SYNOPSIS

       #include <math.h>

       int isnan(real-floating x);

DESCRIPTION

       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 .