[Maxima] Maxima parser and global parameters
macrakis at alum.mit.edu
Tue Jan 15 19:34:45 CST 2008
I believe both Ray's and my proposal are in fact that it be exactly
1/10, that is that its internal form be ((rat simp) 1 10) and its
printed form be 1/10. For that matter, it could be ((rat simp decimal)
1 10) and print as 0.1 -- though users would probably be confused that
1r-1 / 3 printed as 1/30....
On 1/15/08, Richard Fateman <fateman at cs.berkeley.edu> wrote:
> I think there is a kind of problem with Ray's proposal. Namely, if someone
> writing 0.1r0 (or 1/10) expects that the number would be exactly 1/10.
> There is no way in binary floats to do that.
> This is a problem in the perception of the effect, not in implementing
> something, though.
> I agree with Ray that parsing would be relatively easy; between the two of
> us we have written at least 2 such programs recently.:)
> > -----Original Message-----
> > From: maxima-bounces at math.utexas.edu
> > [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Raymond Toy
> > Sent: Tuesday, January 15, 2008 3:06 PM
> > To: Stavros Macrakis
> > Cc: fateman at EECS.Berkeley.EDU; Maxima at math.utexas.edu; van Nek
> > Subject: Re: [Maxima] Maxima parser and global parameters
> > Stavros Macrakis wrote:
> > > 2) use exact notation instead of floating notation for your
> > numbers, e.g.
> > >
> > > block([fpprec:100],
> > > bfloat( sqrt(1000000000000000000001*10^-21) ) );
> > >
> > > 3) use eval_string or parse_string:
> > >
> > > I find (2) the most elegant, but perhaps a little clumsy
> > notationally.
> > >
> > > I wonder if it might be useful to define (e.g.) 1.234x23 ('x' for
> > > exact) to mean precisely the rational number 1234*10^(23-3).
> > >
> > Some time ago, I suggested (in passing) to use 1.234r23 ("r" for
> > rational). I think this (either r or x) would be quite easy to
> > implement. Of course, printing the numbers wouldn't preserve the "r"
> > notation.
> > Ray
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