Hi again, I've got an application I'm working on which needs the ability to handle STL maps and sets containing symbols. In order to be able to use these classes, I have to define an ordering (a less-than operator) for symbols. At the moment I use the 'get_name' method and then compare symbol names as strings, but this isn't really ideal, since it takes a a lot of processing, plus GiNaC is quite happy to tolerate more than one symbol with the same name, so my map/set should be as well. I notice that GiNaC's symbol class has a 'serial number' as one of its properties. Is there any way I can access that value via a public method? Or is there another method suggested for creating sets and maps of symbols? //// Ordering for symbols based on name (there should be a better way)/ *class* symbol_lt{ *public*: bool *operator*()(const GiNaC::symbol &a, const GiNaC::symbol &b) const; }; Cheers JP