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

13       nan, nanf, nanl — return quiet NaN
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SYNOPSIS

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

23       The functionality described on this reference page is aligned with  the
24       ISO C  standard.  Any  conflict between the requirements described here
25       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2008
26       defers to the ISO C standard.
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28       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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34           strtod("NAN()", (char **) NULL)
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36       If  tagp  does  not point to an n-char sequence or an empty string, the
37       function call shall be equivalent to:
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39           strtod("NAN", (char **) NULL)
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41       Function calls to nanf() and nanl() are equivalent to the corresponding
42       function calls to strtof() and strtold().
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RETURN VALUE

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

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

57       None.
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APPLICATION USAGE

60       None.
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RATIONALE

63       None.
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FUTURE DIRECTIONS

66       None.
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SEE ALSO

69       strtod()
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71       The Base Definitions volume of POSIX.1‐2008, <math.h>
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74       Portions  of  this text are reprinted and reproduced in electronic form
75       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
76       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
77       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
78       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
79       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
80       event of any discrepancy between this version and the original IEEE and
81       The Open Group Standard, the original IEEE and The Open Group  Standard
82       is  the  referee document. The original Standard can be obtained online
83       at http://www.unix.org/online.html .
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85       Any typographical or formatting errors that appear  in  this  page  are
86       most likely to have been introduced during the conversion of the source
87       files to man page format. To report such errors,  see  https://www.ker‐
88       nel.org/doc/man-pages/reporting_bugs.html .
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92IEEE/The Open Group                  2013                              NAN(3P)
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