[Python-Dev] Expert floats
ark-mlist at att.net
Wed Mar 31 11:04:12 EST 2004
> > You argued against applying the Scheme rules because that would make
> > marshalling less accurate when the unmarshalling is done on a machine
> > with longer floats.
> I said the 754 committee had that objection.
OK, but either that objection is relevant for Python or it isn't.
> This was discussed on David Hough's numeric-interest mailing list at the
> time Clinger and Steele/White published their float<->string papers, and
> "phooey" was the consensus of the 754 folks on the mailing list at the
Interesting -- I didn't know that. But it would make sense -- they're
probably more interested in cross-platform computational accuracy than they
are in convenience for casual uses.
> I personally don't think decimal strings are a sane way to transport
> binary floats regardless of rounding gimmicks.
> > But on such a machine, 17 digits won't be good enough anyway.
> Doesn't change that 17 digits gets closer then shortest-possible: the art
> of binary fp is about reducing error, not generally about eliminating
> Shortest-possible does go against the spirit of 754 in that respect.
That's a fair criticism. On the other hand, maybe ?!ng is right about the
desirable properties of display for people being different from those for
> > That's what I meant. Rather than 0.47 from exact, I meant 0.47 from
> > the best possible.
> Well, you originally said that in response to my saying that the standard
> doesn't require perfect rounding (and it doesn't), and that the standard
> has different accuracy requirements for different inputs (and it does).
> So now I'm left wondering what your original "I thought that ..." was
> trying to get across.
I don't remember; sorry.
> > Hey, I know some people who write C programs that don't rely on the
> > platform C libraries for anything :-)
> Python would love to grab their I/O implementation then <0.8 wink>.
I think the licensing terms are compatible with Python, if you're serious.
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