округлить до ближайшего целого значения с использованием текущего направления округления (round to nearest integer value using current rounding direction)
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)
lrint, lrintf, lrintl — round to nearest integer value using
current rounding direction
Синопсис (Synopsis)
#include <math.h>
long lrint(double x);
long lrintf(float x);
long lrintl(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 according to 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 error 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 error 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 provide floating-to-integer conversions. They
round according to the current rounding direction. If the rounded
value is outside the range of the return type, the numeric result
is unspecified and the invalid floating-point exception is
raised. When they raise no other floating-point exception and the
result differs from the argument, they raise the inexact
floating-point exception.
Будущие направления (Future directions)
None.
Смотри также (See also)
feclearexcept(3p), fetestexcept(3p), llrint(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.20,
Treatment of Error Conditions for Mathematical Functions,
math.h(0p)
