Re: [Stds-754] Prolegomena to any future decimal discussion

[John R Harrison <johnh@xxxxxxxxxxxxxxxx>]

Hi Michel,

| I'll buy the lexicographic observation, though that is seriously messed
| up by the combination field in all three formats presented here.  (Some
| earlier Intel proposals had tried to deal with this.)

Yes, Peter Tang and I did propose a change in the position of the
combination field when a ZBD-like format was under discussion, with
lexicographic ordering being one motivation.

| I'm amazed however that the sight-reading argument is cited *against* DPD.

Taking "sight reading" to mean more or less instantaneous recognition,
perhaps you are right. Personally, I'm not very good at that for either
format except for some obvious special cases. I was using "sight reading"
loosely to mean any fairly quick back-of-envelope calculation.

To decode a ZBD number, you just need to interpret the 10-bit subfields
as binary numbers, which is a relatively familiar operation. It may take
me a little while, but I can do it on my own. To decode DPD seems to need
more mental gymnastics: according to the setting of one bit, the parts of
the digit are distributed in different places, etc., etc. Perhaps one
gets used to it eventually, but I still need to refer to the tables.

| Many people can read small integers in hex (e.g. up to 256 or so),
| but I should point out that, for DPD, numbers from 000 to 079 stand
| for themselves.

Right, I agree that numbers in this range are easy to recognize in DPD.

John.