[Haskell-cafe] Re: Where is Data.Atom?

Iain Alexander ia at stryx.demon.co.uk
Mon Jul 3 20:33:23 EDT 2006

Another suggestion:

Put your strings in an ordered binary tree (other data structures might also 
work here).

Make your Atom an encoding of the structure of the tree (resp. other 
structure).  This is logically a sequence of bits, 0 for left (less than), 1 for 
right (greater than) - if you terminate this variable-length sequence with 
1, I think it all works out OK.  You then encode this sequence of bits in a 
Word32 (or some other convenient item), with implicit trailing zeros.

root ~> 1[000...]
root.left ~> 01[000...]
root.right ~> 11[000...]

There are clearly some questions such as how unbalanced is the tree 
likely to get (since you can't conveniently rebalance it), and what to do if 
your Atom "overflows", but this might give you something to work with.
Iain Alexander      ia at stryx.demon.co.uk

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