1NAN(3P)                    POSIX Programmer's Manual                   NAN(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       nan, nanf, nanl — return quiet NaN
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SYNOPSIS

15       #include <math.h>
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17       double nan(const char *tagp);
18       float nanf(const char *tagp);
19       long double nanl(const char *tagp);
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DESCRIPTION

22       The functionality described on this reference page is aligned with  the
23       ISO C  standard.  Any  conflict between the requirements described here
24       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2017
25       defers to the ISO C standard.
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27       The function call nan("n-char-sequence") shall be equivalent to:
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30           strtod("NAN(n-char-sequence)", (char **) NULL);
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32       The function call nan("") shall be equivalent to:
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35           strtod("NAN()", (char **) NULL)
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37       If  tagp  does  not point to an n-char sequence or an empty string, the
38       function call shall be equivalent to:
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41           strtod("NAN", (char **) NULL)
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43       Function calls to nanf() and nanl() are equivalent to the corresponding
44       function calls to strtof() and strtold().
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RETURN VALUE

47       These  functions  shall  return a quiet NaN, if available, with content
48       indicated through tagp.
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50       If the implementation does not  support  quiet  NaNs,  these  functions
51       shall return zero.
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ERRORS

54       No errors are defined.
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56       The following sections are informative.
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EXAMPLES

59       None.
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APPLICATION USAGE

62       None.
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RATIONALE

65       None.
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FUTURE DIRECTIONS

68       None.
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SEE ALSO

71       strtod()
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73       The Base Definitions volume of POSIX.1‐2017, <math.h>
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76       Portions  of  this text are reprinted and reproduced in electronic form
77       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
78       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
79       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
80       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
81       event of any discrepancy between this version and the original IEEE and
82       The  Open Group Standard, the original IEEE and The Open Group Standard
83       is the referee document. The original Standard can be  obtained  online
84       at http://www.opengroup.org/unix/online.html .
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86       Any  typographical  or  formatting  errors that appear in this page are
87       most likely to have been introduced during the conversion of the source
88       files  to  man page format. To report such errors, see https://www.ker‐
89       nel.org/doc/man-pages/reporting_bugs.html .
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93IEEE/The Open Group                  2017                              NAN(3P)
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