[Cfp-interest 1721] Re: short hex strings

[Paul Zimmermann]

       Hi David,

for this kind of thing, I find giving a concrete example is very helpful for
the reader to understand the issue. The initial example where 3 can print as
0x2p+1 or 0x3p0 or 0x6p-1 or 0xcp-2 would be nice to add (interestingly, we
can't have 1 for the first hexadecimal digit, assuming rounding is to nearest).

Paul

> Date: Wed, 22 Jul 2020 21:23:17 -0700 (PDT)
> From: David Hough CFP  <pcfp at oakapple.net>
> 
> 
> "295)Binary implementations can choose the hexadecimal digit to the left of the
> decimal-point character so that subsequent digits align to nibble (4-bit) 
> boundaries."
> 
> Action item: Come up with a sentence to add to footnote 295 (as per CFP 
> 1697) to point out the possible numerical differences in output.
> 
> I tried making one sentence, but it got complicated and confusing.
> 
> Suggestion: add these sentences
> 
> This implementation choice affects numerical
> values printed in short hexadecimal formats that can't represent all values 
> exactly.
> Implementations with different conventions about the most significant
> hexadecimal digit will round at different places, affecting the numerical
> value of the hexadecimal result.    Portable code seeking identical results on
> different platforms should avoid such short hexadecimal formats.
> 
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