double rint(doublex);
float rintf(floatx);
long double rintl(long doublex);

DESCRIPTION

These functions shall return the integral value (represented as a
double) nearest x in the direction of the
current rounding mode. The current rounding mode is implementation-defined.

If the current rounding mode rounds toward negative infinity, then
rint() shall be equivalent to floor() . If the current
rounding mode rounds toward positive infinity, then rint() shall
be
equivalent to ceil() .

These functions differ from the nearbyint(), nearbyintf(),
and nearbyintl()
functions only in that they may raise the inexact floating-point exception
if the result differs in value from the argument.

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 integer
(represented as a double precision number) nearest x
in the direction of the current rounding mode.

If
x is NaN, a NaN shall be returned.

If x is ±0 or ±Inf, x shall be returned.

If the correct value would cause overflow, a range error shall occur
and rint(), rintf(), and rintl() shall
return the value of the macro ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL
(with the same sign as x),
respectively.

ERRORS

These functions shall fail if:

Range Error

The result would cause an overflow.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then errno shall be set to [ERANGE]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
then the overflow 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

None.

FUTURE DIRECTIONS

None.

SEE ALSO

abs() , ceil() , feclearexcept() , fetestexcept()
, floor() , isnan() , nearbyint() , 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 .