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Re: [Gcl-devel] Re: [Maxima] float to bfloat
From: |
Camm Maguire |
Subject: |
Re: [Gcl-devel] Re: [Maxima] float to bfloat |
Date: |
30 Jan 2004 13:07:40 -0500 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 |
Greetings, and thanks for your feedback!
"Stavros Macrakis" <address@hidden> writes:
> > My understanding is that the Common Lisp spec is silent on an
> > implementation's treatment of Nan and Inf. If so, and we are
> > implicitly free to implement them in a useful way, I'd be
> > happy to do so for maxima's benefit. Paul, can we define
> > NaN, and Inf as symbols with floating point constant values,
> > and 1/0, -1/0, and 0/0 as analogous rationals? What would be
> > useful rules regarding expressions involving these symbols,
> > beyond NaN - NaN = NaN et. al. mentioned above?
>
> Existing Lisp code may expect 1/0 and 1/0.0 to give errors, not to
> silently return values. It may explicitly catch those errors to do the
> right thing, or it may allow them to be propagated, signalling that its
> result is not valid. Current code also silently returns float-infinity
> for (expt 9.9 9999), though 9.9e9999 gives a floating overflow error.
>
> I don't think it's necessary to have constants NaN, Inf, etc. User code
> can easily enough define such constants, e.g.
>
> (defconstant double-floating-infinity (expt 9.9d0 9999))
> (defconstant double-floating-nan (sin double-floating-infinity))
>
> After all, Common Lisp doesn't have standard constants for pi, sqrt(2),
> etc., does it? I am not sure what you mean by 'rules regarding
> expressions' -- the machine's IEEE float implementation takes care of
> all that. With the above definitions, you have:
>
> (= DFnan DFnan) => nil
> (> Dfinf 0) => t
> (/ 1 inf) => 0.0
>
> though you also have
>
> (/ 1.0 0.0) => Zero divisor error
>
> which I don't think you can turn off in GCL 2.5.0.
>
> To fully integrate NaN/Inf/... into GCL, it would be nice to have
> standard input/output formats and make sure that all floating primitives
> do something useful with them. I believe that integer-encode-float
> works with NaN/Inf, giving an unambiguous return value. Constructing a
> NaN cannot of course be done in the usual way of constructing a float,
> namely (* sign mantissa (expt 2.0 exponent)).
>
OK, so maybe the only useful change might be allowing such items to
print from this perspective. BTW, are the following what you would
expect?
(integer-decode-float (expt 9.9d0 9999))
4503599627370496
972
1
>(integer-decode-float (sin (expt 9.9d0 9999)))
6755399441055744
972
-1
>
Take care,
> _______________________________________________
> Maxima mailing list
> address@hidden
> http://www.math.utexas.edu/mailman/listinfo/maxima
>
>
>
--
Camm Maguire address@hidden
==========================================================================
"The earth is but one country, and mankind its citizens." -- Baha'u'llah
- [Gcl-devel] Re: [Maxima] float to bfloat, Camm Maguire, 2004/01/23
- [Gcl-devel] Re: [Maxima] float to bfloat, Raymond Toy, 2004/01/23
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Camm Maguire, 2004/01/23
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Raymond Toy, 2004/01/23
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Camm Maguire, 2004/01/26
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Richard Fateman, 2004/01/26
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Camm Maguire, 2004/01/26
- RE: [Gcl-devel] Re: [Maxima] float to bfloat, Stavros Macrakis, 2004/01/26
- Re: [Gcl-devel] Re: [Maxima] float to bfloat,
Camm Maguire <=
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Raymond Toy, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Richard Fateman, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Raymond Toy, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Camm Maguire, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Steve Haflich, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Raymond Toy, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Steve Haflich, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Camm Maguire, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Richard Fateman, 2004/01/30
- Re: [Gcl-devel] Re: [Maxima] float to bfloat, Steve Haflich, 2004/01/26