RINT(3)

NAME
rint - and round-to-closest integer functions

SYNOPSIS
#include <math.h>
double
rint(double x);

DESCRIPTION
The rint() function finds the integer (represented as a double precision number) nearest to x in the direction of the prevailing rounding mode.

NOTES
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 stipulation 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 otherwise. 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 predict.

SEE ALSO
abs(3), fabs(3), ceil(3), floor(3), ieee(3), math(3)

HISTORY
A rint() function appeared in AT&T UNIX.