Excerpts from Jeremy Shaw's message of Sun Jun 13 19:16:02 +0200 2010:
Hello,
My idea for solving this problem was to try to use something similar to a kd-tree. I have a proof of concept for 2 keys here:
http://src.seereason.com/haskell-kdmap/
But, to extend it to an arbitrary number of keys may need template haskell.
I tried this. TH changed a little bit so it may be broken. I mapped multi keys to Data.Map Key1 (Data.Map Key 2) http://github.com/MarcWeber/rdmhaskell/ I gave up the project that time due to lack of time and because spending so much time on this project was not worth the time because Postgres and MYSQL already did what I was looking for.. The idea was to model kind of database because I wasn't satisfied with IxSet that time. line 50 shows how to define a combined index on two fields: http://github.com/MarcWeber/rdmhaskell/blob/master/test/TestCase.hs I'm not even sure whether I should recommend reading my code :) All I want to say: Its a little bit of work which is highly appreciated by many Haskellers IMHO. If you start such a project keep posting updates to the list. I'll read them. Marc Weber