Movatterモバイル変換

[0]ホーム

<<<Previous

Home

Next >>>

NAME

lround, lroundf, lroundl - round to nearest integer value

SYNOPSIS

#include <math.h> long lround(doublex); long lroundf(floatx); long lroundl(long doublex);

DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between therequirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO Cstandard.
These functions shall round their argument to the nearest integer value, rounding halfway cases away from zero, regardless ofthe current rounding direction.
An application wishing to check for error situations should seterrno to zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrno is non-zero orfetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

RETURN VALUE

Upon successful completion, these functions shall return the rounded integer value.
^[MX] Ifx is NaN, a domain error shall occur and an unspecified value is returned.
Ifx is +Inf, a domain error shall occur and an unspecified value is returned.
Ifx 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 along, an unspecified value shall be returned.^[MX] Onsystems that support the IEC 60559 Floating-Point option, a domain shall occur; otherwise, a^[CX] domain error may occur.
If the correct value is negative and too large to represent as along, an unspecified value shall be returned.^[MX] Onsystems that support the IEC 60559 Floating-Point option, a domain shall occur; otherwise, a^[CX] domain error may occur.

ERRORS

These functions shall fail if:
Domain Error
^[MX]Thex 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, thenerrno shall be set to [EDOM]. Ifthe integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shallbe 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, thenerrno shall be set to [EDOM]. Ifthe integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shallbe raised.

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) areindependent of each other, but at least one of them must be non-zero.

RATIONALE

These functions differ from thelrint() functions in the default roundingdirection, with thelround() functions rounding halfway cases away from zero and needing not to raise the inexactfloating-point exception for non-integer arguments that round to within the range of the return type.