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LROUND(3P)                 POSIX Programmer's Manual                LROUND(3P)
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
       lround, lroundf, lroundl -- round to nearest integer value
SYNOPSIS
       #include <math.h>
       long lround(double x);
       long lroundf(float x);
       long lroundl(long double x);
DESCRIPTION
       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 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,
       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 a  long,
       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
       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.
       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.
       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 differ from the lrint() functions in the default round-
       ing  direction, with the lround() 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
       None.
SEE ALSO
       feclearexcept(), fetestexcept(), llround()
       The Base Definitions volume of POSIX.1-2008, Section 4.19, Treatment of
       Error Conditions for Mathematical Functions, <math.h>
COPYRIGHT
       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 Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           LROUND(3P)