Hi Simon, The result is that the hash is broken by default, since the string > representation can be changed *after* creation of the object, which > means that the hash value would change as well. There is a ticket fixing > it, though. > > > I think the problem lies in that the hash is calculated when the object > is > > not fully constructed. The hash value should be calculated as the last > part > > of the initialization process, as the hash should be dependent on the > data > > that defines the object. As the "..Algebra.__init__" is expected to be > > placed at the beginning of the initialization code > > Why? Is that a Python convention?
Isn't that a convention of objected-oriented programming? > , I think there should be > > a separate method say "..Algebra._set_hash_" that is executed manually > or > > automatically at the end of the initialization process. > > If it is automatic, then it will probably be at the end of the > initialisation process of Parent.__init__ - but then the problem would > not be solved, because you insist to call Parent.__init__ (indirectly > via ...Ring.__init__) before the initialisation of your object is > completed. > > If it is manual and *has* to be done, then obviously a common > mistake would result, namely to forget initialising the hash. > Yeah, the problem is not easy to solve... Perhaps another idea, that I could easily implement: We could ensure > that calling ...Ring.__init__(..., category=False) would initialise the > ring except for the category framework. Then, the third solution of your > problem would be > def __init__(self, i): > CommutativeRing.__init__(self, i.base_ring(), category=False) > self._ideal = i > self._init_category_(CommutativeRings()) # or whatever is > appropriate > This is similar to my "manual" idea. Would that be acceptable to you? > This seems to be a good solution for all, not just for me. :-) > > Cheers, > Simon > > -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
