NAME

lrint, lrintf, lrintl — round to nearest integer value using current rounding direction

SYNOPSIS

#include <math.h>

long lrint(double x);
long lrintf(float x);
long lrintl(long double x);


DESCRIPTION

^[CX] 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.1-2024 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.

RETURN VALUE

Upon successful completion, these functions shall return the rounded integer value.

^[MX] 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. ^[MX]  On systems that support the IEC 60559 Floating-Point option, a domain error shall occur;  otherwise, a ^[CX]  domain error may occur.

If the correct value is negative and too large to represent as a long, an unspecified value shall be returned. ^[MX]  On systems that support the IEC 60559 Floating-Point option, a domain error shall occur;  otherwise, a ^[CX]  domain error may occur.

ERRORS

These functions shall fail if:

Domain Error

^[MX] 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.

EXAMPLES

None.

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.

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.

FUTURE DIRECTIONS

None.

SEE ALSO

feclearexcept, fetestexcept, llrint

XBD 4.23 Treatment of Error Conditions for Mathematical Functions, <math.h>

CHANGE HISTORY

First released in Issue 6. Derived from the ISO/IEC 9899:1999 standard.

Issue 7

ISO/IEC 9899:1999 standard, Technical Corrigendum 2 #53 (SD5-XSH-ERN-77) is applied.