ROUND(3) Linux Programmer's Manual ROUND(3)
round, roundf, roundl - round to nearest integer, away from zero
double round(double x);
float roundf(float x);
long double roundl(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
round(), roundf(), roundl(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
These functions round x to the nearest integer, but round halfway cases
away from zero (regardless of the current rounding direction), instead
of to the nearest even integer like rint(3).
The rounded integer value. If x is integral or infinite, x itself is
No errors other than EDOM and ERANGE can occur. If x is NaN, then NaN
is returned and errno may be set to EDOM.
POSIX.1-2001 contains text about overflow (which might set errno to
ERANGE, or raise an exception). In practice, the result cannot over-
flow on any current machine, so this error-handling stuff is just non-
sense. (More precisely, overflow can happen only when the maximum
value of the exponent is smaller than the number of mantissa bits. For
the IEEE-754 standard 32-bit and 64-bit floating point numbers the max-
imum value of the exponent is 128 (respectively, 1024), and the number
of mantissa bits is 24 (respectively, 53).)
ceil(3), floor(3), lround(3), nearbyint(3), rint(3), trunc(3)
This page is part of release 3.05 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.