[r6rs-discuss] Confusion over |p

From: Alan Watson <alan>
Date: Fri, 29 Jun 2007 20:07:27 -0500

William D Clinger wrote:
> Are you complaining about the rule that says the absence
> of |p (for an inexact decimal notation) means the same
> as the presence of |53 ?

Yes. However, it doesn't make any difference on common systems that
internally use only IEEE double-precision. But this is Scheme and we
should strive to do better than that.

> Or the rule that says a
> denormalized double precision number really ought to
> be printed with an explicit mantissa width?

Where does it say that?

> Sorry, I meant that p <= 53 would mean x|p is read with
> no loss of accuracy from our agreed-upon meaning of x|p,
> not that it would be read with no loss of accuracy from
> x. For example, 1.1|1 would read as 1.0, not as 1.1|53.

Sorry, I misunderstood you. Yes, if 1.1|1 is 1.0 then I can indeed write
the IEEE single-precision value of 1.1 as 1.1|24 (modulus rounding being
correctly specified).

Subnormals are painful, still.

Regards,

Alan
Received on Fri Jun 29 2007 - 21:07:27 UTC