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

23       The function call nan("n-char-sequence") shall be equivalent to:
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26              strtod("NAN(n-char-sequence)", (char **) NULL);
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28       The function call nan("") shall be equivalent to:
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31              strtod("NAN()", (char **) NULL)
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33       If tagp does not point to an n- char sequence or an empty  string,  the
34       function call shall be equivalent to:
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37              strtod("NAN", (char **) NULL)
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39       Function calls to nanf() and nanl() are equivalent to the corresponding
40       function calls to strtof() and strtold().
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RETURN VALUE

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

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

55       None.
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APPLICATION USAGE

58       None.
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RATIONALE

61       None.
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FUTURE DIRECTIONS

64       None.
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SEE ALSO

67       strtod(),    strtold(),    the    Base    Definitions     volume     of
68       IEEE Std 1003.1-2001, <math.h>
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71       Portions  of  this text are reprinted and reproduced in electronic form
72       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
73       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
74       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
75       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
76       event of any discrepancy between this version and the original IEEE and
77       The  Open Group Standard, the original IEEE and The Open Group Standard
78       is the referee document. The original Standard can be  obtained  online
79       at http://www.opengroup.org/unix/online.html .
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83IEEE/The Open Group                  2003                              NAN(3P)
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