Hello John, Friday, March 3, 2006, 1:10:17 AM, you wrote: JM> Would it be possible to mock up an implementation of this using JM> Data.Generics by chance? so we can use a generalized tree for anything are you know that Data.Generics has run-time overheads and therefore can be several times slower than fixed algorithm or algorithm generated at compile time (for example, by TH) ? JM> <noise> JM> once get get derived generalized tries, I want to try derived JM> generalized huffman (arithmetic?) encoding, derived generalized LZ*, and JM> a derived generalized efficient 'diff' algorithm... JM> </noise> and this will be 1000 times slower that C implementations -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com