double nearbyint(doublex);
float nearbyintf(floatx);
long double nearbyintl(long doublex);

DESCRIPTION

These functions shall round their argument to an integer value in
floating-point format, using the current rounding direction
and without raising the inexact floating-point exception.

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 NaN shall be returned.

If x is ±0, ±0 shall be returned.

If x is ±Inf, x shall be returned.

If the correct value would cause overflow, a range error shall occur
and nearbyint(), nearbyintf(), and
nearbyintl() 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

feclearexcept() , fetestexcept() , 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 .