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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  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, 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 Standard, 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 .