help retrieving / storing info in dictionary or gadfly

[Bryan Webb]

Hello,
    I have a dictionary that has records with keys from 1 to 2^128
I can build a list and sort the keys in order, then search thru the list of
sorted keys.
    If the list has 1,2,3,4,5,7,8,9 and I need to search for 6. 6 is not in
the list , so I need the record that is closest to 6 but not greater than 6.
Is there a way to further index the list of keys to do this ?

Could I use GADFLY to do this.


Any ideas and help would be appreciated.

Thanks
bryan Webb