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 (con-
       sult 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, regard-
       less 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, 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 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 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, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    LROUND(3P)