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NAN(3P)                    POSIX Programmer's Manual                   NAN(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       nan, nanf, nanl - return quiet NaN
SYNOPSIS
       #include <math.h>
       double nan(const char *tagp);
       float nanf(const char *tagp);
       long double nanl(const char *tagp);

DESCRIPTION
       The function call nan("n-char-sequence") shall be equivalent to:

              strtod("NAN(n-char-sequence)", (char **) NULL);
       The function call nan("") shall be equivalent to:

              strtod("NAN()", (char **) NULL)
       If tagp does not point to an n- char sequence or an empty  string,  the
       function call shall be equivalent to:

              strtod("NAN", (char **) NULL)
       Function calls to nanf() and nanl() are equivalent to the corresponding
       function calls to strtof() and strtold().
RETURN VALUE
       These functions shall return a quiet NaN, if  available,  with  content
       indicated through tagp.
       If  the  implementation  does  not  support quiet NaNs, these functions
       shall return zero.
ERRORS
       No errors are defined.
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       strtod(),    strtold(),    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 .

IEEE/The Open Group                  2003                              NAN(3P)