1ISNAN(3P)                  POSIX Programmer's Manual                 ISNAN(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       isnan — test for a NaN
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SYNOPSIS

15       #include <math.h>
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17       int isnan(real-floating x);
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DESCRIPTION

20       The functionality described on this reference page is aligned with  the
21       ISO C  standard.  Any  conflict between the requirements described here
22       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2017
23       defers to the ISO C standard.
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25       The  isnan() macro shall determine whether its argument value is a NaN.
26       First, an argument represented in a format wider than its semantic type
27       is  converted  to its semantic type. Then determination is based on the
28       type of the argument.
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RETURN VALUE

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

35       No errors are defined.
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37       The following sections are informative.
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EXAMPLES

40       None.
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APPLICATION USAGE

43       None.
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RATIONALE

46       None.
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FUTURE DIRECTIONS

49       None.
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SEE ALSO

52       fpclassify(), isfinite(), isinf(), isnormal(), signbit()
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54       The Base Definitions volume of POSIX.1‐2017, <math.h>
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57       Portions  of  this text are reprinted and reproduced in electronic form
58       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
59       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
60       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
61       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
62       event of any discrepancy between this version and the original IEEE and
63       The  Open Group Standard, the original IEEE and The Open Group Standard
64       is the referee document. The original Standard can be  obtained  online
65       at http://www.opengroup.org/unix/online.html .
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67       Any  typographical  or  formatting  errors that appear in this page are
68       most likely to have been introduced during the conversion of the source
69       files  to  man page format. To report such errors, see https://www.ker‐
70       nel.org/doc/man-pages/reporting_bugs.html .
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74IEEE/The Open Group                  2017                            ISNAN(3P)
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