RINT(3) BSD Programmer's Manual RINT(3)
rint - round-to-closest integer functions
The rint() function finds the integer (represented as a double precision
number) nearest to x in the direction of the prevailing rounding mode.
On a VAX, rint(x) is equivalent to adding half to the magnitude and then
rounding towards zero.
In the default rounding mode, to nearest, on a machine that conforms to
IEEE 754, rint(x) is the integer nearest x with the additional stipula-
tion that if |rint(x)-x|=1/2 then rint(x) is even. Other rounding modes
can make rint() act like floor(), or like ceil(), or round towards zero.
Another way to obtain an integer near x is to declare (in C)
double x; int k; k = x;
Most C compilers round x towards 0 to get the integer k, but some do oth-
erwise. If in doubt, use floor(), ceil(), or rint() first, whichever you
intend. Also note that, if x is larger than k can accommodate, the value
of k and the presence or absence of an integer overflow are hard to pre-
abs(3), fabs(3), ceil(3), floor(3), ieee(3), math(3)
A rint() function appeared in Version 6 AT&T UNIX.
4.4BSD December 11, 1993 1