PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

FABS(3P)                  POSIX Programmer's Manual                 FABS(3P)

PROLOG         top

       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         top

       fabs, fabsf, fabsl — absolute value function

SYNOPSIS         top

       #include <math.h>
       double fabs(double x);
       float fabsf(float x);
       long double fabsl(long double x);

DESCRIPTION         top

       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         top

       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         top

       No errors are defined.
       The following sections are informative.

EXAMPLES         top

   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         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       isnan(3p)
       The Base Definitions volume of POSIX.1‐2008, math.h(0p)

COPYRIGHT         top

       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 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 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.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                 2013                            FABS(3P)

Pages that refer to this page: math.h(0p)tgmath.h(0p)abs(3p)