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



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NNAAMMEE
       nan, nanf, nanl -- return quiet NaN

SSYYNNOOPPSSIISS
       #include <math.h>

       double nan(const char *_t_a_g_p);
       float nanf(const char *_t_a_g_p);
       long double nanl(const char *_t_a_g_p);

DDEESSCCRRIIPPTTIIOONN
       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 _n_a_n("_n_-_c_h_a_r_-_s_e_q_u_e_n_c_e") shall be equivalent to:


           strtod("NAN(_n_-_c_h_a_r_-_s_e_q_u_e_n_c_e)", (char **) NULL);

       The function call _n_a_n("") shall be equivalent to:


           strtod("NAN()", (char **) NULL)

       If _t_a_g_p does not point to an _n-cchhaarr sequence or an empty string, the
       function call shall be equivalent to:


           strtod("NAN", (char **) NULL)

       Function calls to _n_a_n_f() and _n_a_n_l() are equivalent to the corresponding
       function calls to _s_t_r_t_o_f() and _s_t_r_t_o_l_d().

RREETTUURRNN VVAALLUUEE
       These functions shall return a quiet NaN, if available, with content
       indicated through _t_a_g_p.

       If the implementation does not support quiet NaNs, these functions
       shall return zero.

EERRRROORRSS
       No errors are defined.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       None.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _s_t_r_t_o_d()

       The Base Definitions volume of POSIX.1-2017, <<mmaatthh..hh>>

CCOOPPYYRRIIGGHHTT
       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 .



IEEE/The Open Group                  2017                               NAN(3)
