округлить до ближайшего целого значения (round to nearest integer 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)
lround, lroundf, lroundl — round to nearest integer value
Синопсис (Synopsis)
#include <math.h>
long lround(double x);
long lroundf(float x);
long lroundl(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 round their argument to the nearest integer
value, rounding halfway cases away from zero, regardless of the
current rounding direction.
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
rounded integer value.
If x is NaN, a domain error shall occur and an unspecified value
is returned.
If x is +Inf, a domain error shall occur and an unspecified value
is returned.
If x is -Inf, a domain error shall occur and an unspecified value
is returned.
If the correct value is positive and too large to represent as a
long, an unspecified value shall be returned. On systems that
support the IEC 60559 Floating-Point option, a domain shall
occur; otherwise, a domain error may occur.
If the correct value is negative and too large to represent as a
long, an unspecified value shall be returned. On systems that
support the IEC 60559 Floating-Point option, a domain shall
occur; otherwise, a domain error may occur.
Ошибки (Error)
These functions shall fail if:
Domain Error
The x argument is NaN or ±Inf, or the correct value
is not representable as an integer.
If the integer expression (math_errhandling &
MATH_ERRNO) is non-zero, then errno shall be set to
[EDOM]. If the integer expression (math_errhandling
& MATH_ERREXCEPT) is non-zero, then the invalid
floating-point exception shall be raised.
These functions may fail if:
Domain Error
The correct value is not representable as an integer.
If the integer expression (math_errhandling &
MATH_ERRNO) is non-zero, then errno shall be set to
[EDOM]. If the integer expression (math_errhandling
& MATH_ERREXCEPT) is non-zero, then the invalid
floating-point exception shall be raised.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
On error, the expressions (math_errhandling & MATH_ERRNO) and
(math_errhandling & MATH_ERREXCEPT) are independent of each
other, but at least one of them must be non-zero.
Обоснование (Rationale)
These functions differ from the lrint() functions in the default
rounding direction, with the lround() functions rounding halfway
cases away from zero and needing not to raise the inexact
floating-point exception for non-integer arguments that round to
within the range of the return type.
Будущие направления (Future directions)
None.
Смотри также (See also)
feclearexcept(3p), fetestexcept(3p), llround(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.20,
Treatment of Error Conditions for Mathematical Functions,
math.h(0p)
