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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: 26 Jan 2004 19:27:38 -0500
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

Greetings!

Richard Fateman <address@hidden> writes:

> test integer-decode-float  on NaN, Infinity, etc.
> before you decide your program is correct.   I think that
> such non-numbers should be "bigfloated" into symbols / gensyms
> with appropriate properties.
> e.g. NaN - NaN  = NaN     (not 0).
> Complicates matters!
> RJF
> 

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? 

Take care,

> 
> Camm Maguire wrote:
> 
> >Greetings!
> >
> >Raymond Toy <address@hidden> writes:
> >
> >
> >>>>>>>"Camm" == Camm Maguire <address@hidden> writes:
> >>>>>>>
> >>    Camm> I don't think this is the case:
> >>
> >>My apologies.  I didn't test it.  I used to have problems with gcl's
> >>float reader/printer, but I guess you've fixed those.  Nice!
> >>
> >>    Camm> OK, will consider after Stavros gets a chance to look into things 
> >> next
> >>    Camm> week.  Thanks again to all!
> >>
> >>FWIW, I ran your test function on cmucl.  It passes the test case
> >>(test-f 1d0 10).  Also, there were a couple of minor bugs.  float
> >>should take the 2nd arg, otherwise it converts to single-float be
> >>default.  This was messing up cmucl. :-)
> >>
> >>
> >
> >Thanks.  Just a clarification here, this test also passes with GCL's
> >current rationalize, just not (yet) with the proposed improved one.
> >
> >Take care,
> >
> >
> >>(defun test-f (x i)
> >>  (multiple-value-bind
> >>      (q r s)
> >>      (integer-decode-float x)
> >>    (format t "~S~%" x)
> >>    (and (eql x (float (* q (expt 2 r)) x))
> >>         (eql (float (rationalize x) x) x)
> >>         (if (> i 0)
> >>             (test-f (float (* (+ q 1) (expt 2 r)) x) (- i 1))
> >>             t))))
> >>
> >>Ray
> >>
> >>
> >>
> >>
> >>
> >
> >
> 
> _______________________________________________
> 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




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