Nathann Cohen wrote:
> Hello !!!
> 
> I always have to include in my graphs functions some part of code to 
> deal with the fact that for undirected graphs edges can be returned as 
> (u,v) or as (v,u), which my code does not like.... Isn't there a Sage a 
> type of variable which is both immutable and not ordered ?
> 
> I'd love to have something like Set(u,v) but I also need it to be 
> immutable, hashable, etc... ;-)
> 

frozenset would be the python answer to your question.  I'm not sure if 
Sage has a better answer:

http://docs.python.org/library/stdtypes.html#set-types-set-frozenset

Jason


-- 
Jason Grout


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