NAME
lround, lroundf, lroundl - round to nearest integer value
SYNOPSIS
#include <math.h>
long lround(double x);
long lroundf(float x);
long lroundl(long double x);
DESCRIPTION
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,
a domain error shall occur and an unspecified value is returned.
If the correct value is negative and too large to represent as a long,
a domain error shall occur and an unspecified value is returned.
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.
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 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.
FUTURE DIRECTIONS
None.
SEE ALSO
feclearexcept() , fetestexcept() , llround() , the Base Definitions
volume of IEEE Std 1003.1-2001, Section 4.18, 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, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .