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Re: operation of 'round' function


From: Eli Zaretskii
Subject: Re: operation of 'round' function
Date: Fri, 08 Feb 2002 12:22:13 +0200

> From: David Kastrup <address@hidden>
> Newsgroups: gnu.emacs.bug
> Date: 07 Feb 2002 17:13:16 +0100
> 
> So the doc string should be amended to read
> "Return the nearest integer to ARG.  In case ARG lies equally close to
> the next and previous integer"
> and then we'd need the proper statement, something like
> a) "the behaviour depends on the floating point implementation of the
> underlying machine Emacs is running on"
> b) "the next even integer is chosen in compliance with IEEE
> arithmetic"
> c) "Emacs consults the variable rounding-direction which
> can take on the values 't, 'nil or 'randomly meaning..."

Thanks for the suggestions.  The correct interpretation is a).  I
fixed the doc string by borrowing what the ELisp reference already
says:

    Rounding a value equidistant between two integers may choose the
    integer closer to zero, or it may prefer an even integer, depending on
    your machine.  For example, \(round 2.5\) can return 3 on some
    systems, but 3 on others.

The Emacs primitive simply calls `rint', which works according to the
current rounding mode.



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