lrint (3p) - Linux Manuals

lrint: round to nearest integer value using current

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.

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

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.

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, a domain error shall occur and an unspecified value is returned.

If the correct value is negative and too large to represent as a long, a domain error shall occur and an unspecified value is returned.

ERRORS

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.

The following sections are informative.

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.

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .