long lround(doublex);
long lroundf(floatx);
long lroundl(long doublex);

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 .