posix man page for fabs

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 correspond-
       ing 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 Technol-
       ogy -- 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 Stan-
       dard 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)