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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
LROUND(3P) POSIX Programmer's Manual LROUND(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.
lround, lroundf, lroundl — round to nearest integer value
#include <math.h>
long lround(double x);
long lroundf(float x);
long lroundl(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 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.
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 Floating-Point option, a domain 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 Floating-Point option, a domain shall occur;
otherwise, a domain error may occur.
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.
None.
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.
These functions differ from the lrint() functions in the default
rounding direction, with the lround() functions rounding halfway
cases away from zero and needing not to raise the inexact floating-
point exception for non-integer arguments that round to within the
range of the return type.
None.
feclearexcept(3p), fetestexcept(3p), llround(3p)
The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment
of Error Conditions for Mathematical Functions, 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.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.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 LROUND(3P)
Pages that refer to this page: math.h(0p), llround(3p)