NAN

Section: POSIX Programmer's Manual (3P)
Updated: 2017
Index Return to Main Contents

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 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.1-2017 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.

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

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 .

This document was created by man2html, using the manual pages.
Time: 06:23:06 GMT, May 09, 2021

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PROLOG

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

EXAMPLES

APPLICATION USAGE

RATIONALE

FUTURE DIRECTIONS

SEE ALSO

COPYRIGHT

Index