функция потолка: наименьшее целое значение не меньше аргумента (ceiling function: smallest integral value not less than argument)
Имя (Name)
ceil, ceilf, ceill - ceiling function: smallest integral value
not less than argument
Синопсис (Synopsis)
#include <math.h>
double ceil(double x);
float ceilf(float x);
long double ceill(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
ceilf(), ceill():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Описание (Description)
These functions return the smallest integral value that is not
less than x.
For example, ceil(0.5) is 1.0, and ceil(-0.5) is 0.0.
Возвращаемое значение (Return value)
These functions return the ceiling of x.
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.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ceil(), ceilf(), ceill() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.
Примечание (Note)
SUSv2 and POSIX.1-2001 contain 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).)
The integral value returned by these functions may be too large
to store in an integer type (int, long, etc.). To avoid an
overflow, which will produce undefined results, an application
should perform a range check on the returned value before
assigning it to an integer type.
Смотри также (See also)
floor(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3)
