Re: Float comparison

Beej Jorgensen <beej@xxxxxxx> writes:
Keith Thompson <kst-u@xxxxxxx> wrote:
Beej Jorgensen <beej@xxxxxxx> writes:
Keith Thompson <kst-u@xxxxxxx> wrote:
The model, at least if you look at just those two paragraphs
[5.2.4.2.2p1-2], defines a mapping from floating-point values to real
values, not vice versa.

Hey, Keith--sorry to bring this back up, but I'm not following exactly
what you mean here. Can I not take the digits of a real number and use
the model to construct a floating point number?

Not in general, no, but it depends on what kind of mapping you're
looking for.

It was the "in general" part that I was missing from the previous post.
It seems to me the standard does define a mapping from *representable*
reals to floating point values, yes? (Via The Model.)

Sure. Well, it does so implicitly. The Model defines a mapping that
specifies, for each FP value, what its real value is. You can
trivially invert that mapping to get a mapping from a subset of the
reals to FP values. INAIAU.

--
Keith Thompson (The_Other_Keith) kst-u@xxxxxxx <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
.

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