fabs, floor, ceil, rint - absolute value, floor, ceiling, and
Fabs returns the absolute value |x|.
Floor returns the largest integer no greater than x.
Ceil returns the smallest integer no less than x.
Rint returns the integer
(represented as a double precision number)
nearest 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 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.
abs(3), ieee(3), libm(3)