PROLOG  NAME  SYNOPSIS  DESCRIPTION  RETURN VALUE  ERRORS  EXAMPLES  APPLICATION USAGE  RATIONALE  FUTURE DIRECTIONS  SEE ALSO  COPYRIGHT 

LROUND(3P) POSIX Programmer's Manual LROUND(3P)
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.
lround, lroundf, lroundl — round to nearest integer value
#include <math.h> long lround(double x); long lroundf(float x); long lroundl(long double x);
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.1‐2008 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 nonzero or fetestexcept(FE_INVALID  FE_DIVBYZERO  FE_OVERFLOW  FE_UNDERFLOW) is nonzero, an error has occurred.
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 FloatingPoint 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 FloatingPoint option, a domain shall occur; otherwise, a domain error may occur.
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 nonzero, then errno shall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is nonzero, then the invalid floatingpoint 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 nonzero, then errno shall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is nonzero, then the invalid floatingpoint exception shall be raised. The following sections are informative.
None.
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 nonzero.
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 noninteger arguments that round to within the range of the return type.
None.
feclearexcept(3p), fetestexcept(3p), llround(3p) The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of Error Conditions for Mathematical Functions, math.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology  Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.12008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/manpages/reporting_bugs.html .
IEEE/The Open Group 2013 LROUND(3P)
Pages that refer to this page: math.h(0p), llround(3p)