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

FABS(3P) POSIX Programmer's Manual FABS(3P)
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.
fabs, fabsf, fabsl — absolute value function
#include <math.h> double fabs(double x); float fabsf(float x); long double fabsl(long double x);
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.
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.
No errors are defined. The following sections are informative.
Computing the 1Norm of a FloatingPoint Vector This example shows the use of fabs() to compute the 1norm 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 ith component of v (0≤i<n). #include <math.h> double norm1(const double v[], const int n) { int i; double n1_v; /* 1norm of v */ n1_v = 0; for (i=0; i<n; i++) { n1_v += fabs (v[i]); } return n1_v; }
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isnan(3p) The Base Definitions volume of POSIX.1‐2008, math.h(0p)
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.12008 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/manpages/reporting_bugs.html .
IEEE/The Open Group 2013 FABS(3P)