
LROUND(P) POSIX Programmer's Manual LROUND(P)
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 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, 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 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 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 floatingpoint exception for noninteger 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 1003.12001, Section 4.18, Treatment of Error Conditions for Mathematical Func
tions, <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) 20012003 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 orig
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 LROUND(P) 
