[thelist] Unique combination numbering
David T-G
davidtg-thelist at justpickone.org
Fri May 7 09:58:01 CDT 2004
João, et al --
...and then João Verde said...
%
% The situation:
% =========
%
% I have a form with a field for which there are 5 possible checkboxes.
%
% [EXAMPLE]
% Water: [ ] River [ ] Lagoon [ ] Pool [ ] Sea [ ] Other
% [/EXAMPLE]
%
% You can check them all, none, or any combination of the 5.
Since each of these places can hold one of two values, I would represent
it in binary; you can even use a smallint (two to the eighth power = 256
unique values) to do it.
W R L P S bin dec
. . . . . 00000 0 + 0 + 0 + 0 + 0 = 0
. . . . x 00001 0 + 0 + 0 + 0 + 1 = 1
. x . x . 01010 0 + 8 + 0 + 2 + 0 = 10
x . . . . 10000 16 + 0 + 0 + 0 + 0 = 16
x x x x x 11111 16 + 8 + 4 + 2 + 1 = 31
[Note that you show 'Other' as well; going from 2^5 to 2^6 is left as an
exercise for the student if necessary.]
All you have to do is keep dividing the number you've stored by two to
see what input you had. There may even be some bit-shifting or dec<->bin
conversions in the language you're using to make encoding and decoding
easier.
HTH & HAND
:-D
--
David T-G
davidtg at justpickone.org
http://justpickone.org/davidtg/ Shpx gur Pbzzhavpngvbaf Qrprapl Npg!
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