]> On Thursday 06 November 2003 18:41, Harrison, John R wrote: > Does anyone know a representation of finite sets over an orderable > polymorphic type that's (1) efficient and (2) canonical? Even better would > be a CAML or OCaml implementation. More precisely I'm looking for: > > 1. Log-time lookup and insertion, and linear-time union, intersection > etc. > > 2. Equal sets are represented by the same object. > > For example, ordered lists satisfy (2) but only part of (1), while all the > variants of balanced trees I can remember that satisfy (1) --- AVL trees > etc. --- fail (2). It will be pretty hard to get 2. Not unless you are using disjoint sets :) You basically want O(1) for set equality, I suppose. Now, I think you wish to insert a new set in amortized O(lgn) time like in a disjoint set implementation. You can still use edison, isn't it good enough for you? I'm saying this, because I don't think there is a straightforward functional way. I have on my mind 2-universal hash functions, but here I am facing bugs of my own. I'm not in the structure monster mode right now it seems :) Cheers, -- Eray Ozkural (exa) <erayo@cs.bilkent.edu.tr> Comp. Sci. Dept., Bilkent University, Ankara KDE Project: http://www.kde.org www: http://www.cs.bilkent.edu.tr/~erayo Malfunction: http://mp3.com/ariza GPG public key fingerprint: 360C 852F 88B0 A745 F31B EA0F 7C07 AE16 874D 539C ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners