On Apr 24, 2008, at 11:33 AM, Adrian Hey wrote:
Also, if you're likely to be using union/intersection a lot you should know that Data.Map/Set are very slow for this because they use the not efficient hedge algorithm :-)
OK, I'm going to bite here: What's the efficient algorithm for union on balanced trees, given that hedge union was chosen as being more efficient than naive alternatives (split and merge, repeated insertion)? My going hypothesis has been "hedge union is an inefficient algorithm, except that it's better than all those other inefficient algorithms". For IntSet/IntMap of course the split structure of the tree is fixed (we can think of these as being compressed versions of a complete binary tree) and union and intersection are quite efficient. -Jan-Willem Maessen