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 (con-
       sult 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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                       NAN(3P)