к ближайшему целому значению (to-nearest integral value)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
rint, rintf, rintl — round-to-nearest integral value
Синопсис (Synopsis)
#include <math.h>
double rint(double x);
float rintf(float x);
long double rintl(long double x);
Описание (Description)
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
These functions shall return the integral value (represented as a
double) nearest x in the direction of the current rounding mode.
The current rounding mode is implementation-defined.
If the current rounding mode rounds toward negative infinity,
then rint() shall be equivalent to floor(3p). If the current
rounding mode rounds toward positive infinity, then rint() shall
be equivalent to ceil(3p). If the current rounding mode rounds
towards zero, then rint() shall be equivalent to trunc(3p). If
the current rounding mode rounds towards nearest, then rint()
differs from round(3p) in that halfway cases are rounded to even
rather than away from zero.
These functions differ from the nearbyint(), nearbyintf(), and
nearbyintl() functions only in that they may raise the inexact
floating-point exception if the result differs in value from the
argument.
An application wishing to check for error situations should set
errno to zero and call feclearexcept(FE_ALL_EXCEPT) before
calling these functions. On return, if errno is non-zero or
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW |
FE_UNDERFLOW) is non-zero, an error has occurred.
Возвращаемое значение (Return value)
Upon successful completion, these functions shall return the
integer (represented as a double precision number) nearest x in
the direction of the current rounding mode. The result shall
have the same sign as x.
If x is NaN, a NaN shall be returned.
If x is ±0 or ±Inf, x shall be returned.
Ошибки (Error)
No errors are defined.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
The integral value returned by these functions need not be
expressible as an intmax_t. The return value should be tested
before assigning it to an integer type to avoid the undefined
results of an integer overflow.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
abs(3p), ceil(3p), feclearexcept(3p), fetestexcept(3p),
floor(3p), isnan(3p), nearbyint(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.20,
Treatment of Error Conditions for Mathematical Functions,
math.h(0p)
