RE: Incrementing Character Fields

["Brendan Bispham" <midrangel@xxxxxxxxxxxxxxxxxx>]

Thanks Dave, I thought you might respond!

I think you've got it to the smallest, however I think that if I use base 26
for the first character and base 32 for the rest, it still only comes to 7
characters.

I say this on an assumption that the machine will prefer base 32
calculations. I've written a DIV/MVR combination but thought that in the
future a binary operation might be faster (I seem to remember that in other
languages you could replace a DIV 32 with a 'move binary point 5 positions
left' operation?).

Brendan Bispham


-----Original Message-----

You can convert any 10 digit base 10 number to a valid object name using a
maximum of 7 significant characters. An object name has to begin with A-Z,
$, # or @. This gives you 29 possibilities for character 1. Subsequent
characters can be any of these plus 0-9, _ and . giving you 41
possibilities for each character in positions 2 - 10. So let A through Z
represent 0 through 26, $ represent 27, # represent 28, @ represent 29, 0
through 9 represent 30 through 39, _ represent 40 and . represent 41.

As an object name is (a maximum of) 10 characters we can represent any
number that will convert to base 41 as long as the leading digit does not
go above 29. This gives us a highest number of (30(41**9))-1. So a decimal
value of 9,999,999,999 would give 2-4-12-35-26-40-0 in base 41. This
translates to "BDL5Z_0". Putting in the leading "zeroes" we get an object
name of AAABDL5Z_0.

Incidentally, Leif's solution of using a 4 byte binary representation not
only fails to produce valid object names but can't represent numbers higher
than 4,294,967,295. Decimal 9,999,999,999 requires 9 digits in hexadecimal.

Dave Kahn, ABB Steward Ltd.

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