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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 dif-
       fer (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
       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  feclearex-
       cept(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 excep-
       tion 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  indepen-
       dent of each other, but at least one of them must be non-zero.

RATIONALE
       These  functions  differ  from the lrint() functions in the default rounding direction, with the lround() func-
       tions 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 IEEE Std 1003.1-2001, Section 4.18,
       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, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, 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 .



IEEE/The Open Group                  2003                           LROUND(3P)