округлить до ближайшего целого числа, отличного от нуля (round to nearest integer, away from zero)
Имя (Name)
round, roundf, roundl - round to nearest integer, away from zero
Синопсис (Synopsis)
#include <math.h>
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():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
Описание (Description)
These functions round x to the nearest integer, but round halfway
cases away from zero (regardless of the current rounding
direction, see fenv(3)), instead of to the nearest even integer
like rint(3).
For example, round(0.5) is 1.0, and round(-0.5) is -1.0.
Возвращаемое значение (Return value)
These functions return the rounded integer value.
If x is integral, +0, -0, NaN, or infinite, x itself is returned.
Ошибки (Error)
No errors occur. POSIX.1-2001 documents a range error for
overflows, but see NOTES.
Версии (Versions)
These functions first appeared in glibc in version 2.1.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│round(), roundf(), roundl() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
C99, POSIX.1-2001, POSIX.1-2008.
Примечание (Note)
POSIX.1-2001 contains text about overflow (which might set errno
to ERANGE, or raise an FE_OVERFLOW exception). In practice, the
result cannot overflow on any current machine, so this error-
handling stuff is just nonsense. (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 maximum value of the
exponent is 128 (respectively, 1024), and the number of mantissa
bits is 24 (respectively, 53).)
If you want to store the rounded value in an integer type, you
probably want to use one of the functions described in lround(3)
instead.
Смотри также (See also)
ceil(3), floor(3), lround(3), nearbyint(3), rint(3), trunc(3)
