FABS(3)                    POSIX Programmer's Manual                   FABS(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
       fabs, fabsf, fabsl -- absolute value function

SSYYNNOOPPSSIISS
       #include <math.h>

       double fabs(double _x);
       float fabsf(float _x);
       long double fabsl(long double _x);

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.

       These functions shall compute the absolute value of their argument
       _x,|_x|.

RREETTUURRNN VVAALLUUEE
       Upon successful completion, these functions shall return the absolute
       value of _x.

       If _x is NaN, a NaN shall be returned.

       If _x is +-0, +0 shall be returned.

       If _x is +-Inf, +Inf shall be returned.

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
   CCoommppuuttiinngg tthhee 11--NNoorrmm ooff aa FFllooaattiinngg--PPooiinntt VVeeccttoorr
       This example shows the use of _f_a_b_s() to compute the 1-norm of a vector
       defined as follows:


           norm1(v) = |v[0]| + |v[1]| + ... + |v[n-1]|

       where |_x| denotes the absolute value of _x, _n denotes the vector's
       dimension _v[_i] denotes the _i-th component of _v (0<=_i<_n).


           #include <math.h>

           double
           norm1(const double v[], const int n)
           {
               int     i;
               double  n1_v;  /* 1-norm of v */

               n1_v = 0;
               for (i=0; i<n; i++) {
                   n1_v += fabs (v[i]);
               }

               return n1_v;
           }

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _i_s_n_a_n()

       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                              FABS(3)
