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FABS(3P)                   POSIX Programmer's Manual                  FABS(3P)
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
       fabs, fabsf, fabsl -- absolute value function
SYNOPSIS
       #include <math.h>
       double fabs(double x);
       float fabsf(float x);
       long double fabsl(long double x);
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.
       These  functions  shall  compute  the  absolute value of their argument
       x,|x|.
RETURN VALUE
       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.
ERRORS
       No errors are defined.
       The following sections are informative.
EXAMPLES
   Computing the 1-Norm of a Floating-Point Vector
       This  example shows the use of fabs() 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;
           }
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       isnan()
       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 Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  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  Standard
       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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                             FABS(3P)