posix man page for nan

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 correspond-
       ing 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 functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here
       and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

       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()

       The Base Definitions volume of POSIX.1-2008, <math.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C)  2013  by	the  Institute	of
       Electrical and Electronics Engineers, Inc and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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 Stan-
       dard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE
/The Open Group						       2013								   NAN(3P)