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Re: Strange division using mixed integers and floats
From: |
Lars Brinkhoff |
Subject: |
Re: Strange division using mixed integers and floats |
Date: |
28 Apr 2004 15:20:56 +0200 |
User-agent: |
Gnus/5.0808 (Gnus v5.8.8) Emacs/20.7 |
David Kastrup <address@hidden> writes:
> Richard Stallman <address@hidden> writes:
> > But this behaviour is *highly* confusing:
> > (/ 5 4 2.3) => 0.4347826086956522
> > Cf. (/ 5 4.0 2.3) => 0.5434782608695653
> >
> > We could change the functions to convert the arguments to floating
> > point at the start if any is floating point. Is there any reason
> > not to do that?
>
> Efficiency? Lisp is not a statically typed language. We don't know
> the type of the arguments until after they have been evaluated. We
> would have to store all intermediate results away before being
> allowed to do the first operation.
Seems like it's only a matter of changing arith_driver to do
if (FLOATP (val))
{
if (code == Adiv)
return float_arith_driver (0.0, 0, code, nargs, args);
else
return float_arith_driver ((double) accum, argnum, code,
nargs, args);
}
or similar. Loss of efficiency should be small.
> Also (/ 5 4 2.3) would no longer be equivalent to (/ (/ 5 4) 2.3).
That's more significant, as it's a user-visible change.
--
Lars Brinkhoff, Services for Unix, Linux, GCC, HTTP
Brinkhoff Consulting http://www.brinkhoff.se/