LRINT
Section: POSIX Programmer's Manual (3P)
Updated: 2017
Page Index
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
lrint,
lrintf,
lrintl
 round to nearest integer value using current rounding direction
SYNOPSIS
#include <math.h>
long lrint(double x);
long lrintf(float x);
long lrintl(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.12017 defers to the ISO C standard.
These functions shall round their argument to the nearest integer
value, rounding according to 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 nonzero or fetestexcept(FE_INVALID  FE_DIVBYZERO 
FE_OVERFLOW  FE_UNDERFLOW) is nonzero, 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,
an unspecified value shall be returned.
On systems that support the IEC 60559 FloatingPoint option, a domain
error shall occur;
otherwise, a
domain
error may occur.
If the correct value is negative and too large to represent as a
long,
an unspecified value shall be returned.
On systems that support the IEC 60559 FloatingPoint option, a domain
error shall occur;
otherwise, 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
nonzero, then
errno
shall be set to
[EDOM].
If the integer expression (math_errhandling & MATH_ERREXCEPT) is
nonzero, then the invalid floatingpoint 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
nonzero, then
errno
shall be set to
[EDOM].
If the integer expression (math_errhandling & MATH_ERREXCEPT) is
nonzero, then the invalid floatingpoint 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 nonzero.
RATIONALE
These functions provide floatingtointeger conversions. They round
according to the current rounding direction. If the rounded value is
outside the range of the return type, the numeric result is unspecified
and the invalid floatingpoint exception is raised. When they raise no
other floatingpoint exception and the result differs from the
argument, they raise the inexact floatingpoint exception.
FUTURE DIRECTIONS
None.
SEE ALSO
feclearexcept(),
fetestexcept(),
llrint()
The Base Definitions volume of POSIX.12017,
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 1003.12017, 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/manpages/reporting_bugs.html .