LLROUND(3P) POSIX Programmer's Manual LLROUND(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
llround, llroundf, llroundl — round to nearest integer value
SYNOPSIS
#include <math.h>
long long llround(double x);
long long llroundf(float x);
long long llroundl(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 round their argument to the nearest integer
value, rounding halfway cases away from zero, regardless of the current
rounding direction.
An application wishing to check for error situations should set errno
to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
occurred.
RETURN VALUE
Upon successful completion, these functions shall return the rounded
integer value.
If x is NaN, a domain error shall occur, and an unspecified value is
returned.
If x is +Inf, a domain error shall occur and an unspecified value is
returned.
If x is −Inf, a domain error shall occur and an unspecified value is
returned.
If the correct value is positive and too large to represent as a long
long, an unspecified value shall be returned. On systems that support
the IEC 60559 Floating-Point option, a domain error shall occur; other‐
wise, a domain error may occur.
If the correct value is negative and too large to represent as a long
long, an unspecified value shall be returned. On systems that support
the IEC 60559 Floating-Point option, a domain error shall occur; other‐
wise, a domain error may occur.
ERRORS
These functions shall fail if:
Domain Error
The x argument is NaN or ±Inf, or the correct value is not
representable as an integer.
If the integer expression (math_errhandling & MATH_ERRNO)
is non-zero, then errno shall be set to [EDOM]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is
non-zero, then the invalid floating-point exception shall
be raised.
These functions may fail if:
Domain Error
The correct value is not representable as an integer.
If the integer expression (math_errhandling & MATH_ERRNO)
is non-zero, then errno shall be set to [EDOM]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is
non-zero, then the invalid floating-point exception shall
be raised.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
On error, the expressions (math_errhandling & MATH_ERRNO) and
(math_errhandling & MATH_ERREXCEPT) are independent of each other, but
at least one of them must be non-zero.
RATIONALE
These functions differ from the llrint() functions in that the default
rounding direction for the llround() functions round halfway cases away
from zero and need not raise the inexact floating-point exception for
non-integer arguments that round to within the range of the return
type.
FUTURE DIRECTIONS
None.
SEE ALSOfeclearexcept(), fetestexcept(), lround()
The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of
Error Conditions for Mathematical Functions, <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 LLROUND(3P)
