RINT
Section: POSIX Programmer's Manual (3P)
Updated: 2017
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This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
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NAME
rint,
rintf,
rintl
--- round-to-nearest integral value
SYNOPSIS
#include <math.h>
double rint(double x);
float rintf(float x);
long double rintl(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.1-2017 defers to the ISO C standard.
These functions shall return the integral value (represented as a
double)
nearest
x
in the direction of the current rounding mode. The current rounding
mode is implementation-defined.
If the current rounding mode rounds toward negative infinity, then
rint()
shall be equivalent to
floor().
If the current rounding mode rounds toward positive infinity, then
rint()
shall be equivalent to
ceil().
If the current rounding mode rounds towards zero, then
rint()
shall be equivalent to
trunc().
If the current rounding mode rounds towards nearest, then
rint()
differs from
round()
in that halfway cases are rounded to even rather than away from zero.
These functions differ from the
nearbyint(),
nearbyintf(),
and
nearbyintl()
functions only in that they may raise the inexact floating-point
exception if the result differs in value from the argument.
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 integer
(represented as a double precision number) nearest
x
in the direction of the current rounding mode.
The result shall have the same sign as
x.
If
x
is NaN, a NaN shall be returned.
If
x
is ±0 or ±Inf,
x
shall be returned.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
The integral value returned by these functions need not be expressible
as an
intmax_t.
The return value should be tested before assigning it to an integer type
to avoid the undefined results of an integer overflow.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
abs(),
ceil(),
feclearexcept(),
fetestexcept(),
floor(),
isnan(),
nearbyint()
The Base Definitions volume of POSIX.1-2017,
Section 4.20, Treatment of Error Conditions for Mathematical Functions,
<math.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
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.opengroup.org/unix/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 .