Movatterモバイル変換

lround(3p) — Linux manual page

LROUND(3P)              POSIX Programmer's ManualLROUND(3P)

PROLOG        top

       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        top

       lround, lroundf, lroundl — round to nearest integer value

SYNOPSIS        top

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

DESCRIPTION        top

       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 halfway cases away from zero, regardless of the       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        top

       Upon successful completion, these functions shall return the       rounded integer value.       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.  On systems that       support the IEC 60559 Floating-Point option, a domain shall occur;       otherwise, a domain error may occur.       If the correct value is negative and too large to represent as along, an unspecified value shall be returned.  On systems that       support the IEC 60559 Floating-Point option, a domain shall occur;       otherwise, a domain error may occur.

ERRORS        top

       These functions shall fail if:       Domain Error                   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].  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, thenerrno 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        top

       None.

APPLICATION USAGE        top

       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        top

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

FUTURE DIRECTIONS        top

       None.

SEE ALSO        top

feclearexcept(3p),fetestexcept(3p),llround(3p)       The Base Definitions volume of POSIX.1‐2017,Section 4.20,Treatment of Error Conditions for Mathematical Functions,math.h(0p)

COPYRIGHT        top

       Portions of this text are reprinted and reproduced in electronic       form from IEEE Std 1003.1-2017, Standard for Information       Technology -- Portable Operating System Interface (POSIX), The       Open Group Base Specifications Issue 7, 2018 Edition, Copyright       (C) 2018 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 athttp://www.opengroup.org/unix/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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group                2017LROUND(3P)

Pages that refer to this page:math.h(0p), llround(3p)

HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH.