Hey, > > I'm writing code for a new ring and my element is derived from > > RingElement and the parent has category Rings. > > Where can I find the code used by __eq__ ? (I searched now for some > > while, but wasn't able to find it). In particular I'm interested in the > > part which uses the coercion model. > > See src/structure/element.pyx. You need to look for __cmp__ and > __richcmp__; the use of __eq__, __neq__, __le__ etc is deprecated in > Sage, if I understand correctly. > > No, the opposite. the rich comparisons __eq__, __lt__, etc. are what should be used in place of __cmp__ in order to be more python3 compliant (as __cmp__ is deprecated in python3). In cython, I believe we must use __richcmp__ (which merges the rich comparisons into 1 function).
> In any case, you should have a look at the *comments* in element.pyx (I > am afraid it is not docstrings...), which give some useful hints. > > In particular, you can see that if your derived class is a *Python* class, > then you should just implement __cmp__, and then the coercion framework > will (or should...) automatically make sure that the input of your __cmp__ > method will always belong to the same parent. > But if your derived class is a *Cython* class, then, you *must* copy the > __cmp__ code and the __richcmp__ code from sage.structure.element, and > then provide methods _cmp_c_impl and/or _richcmp_c_impl. Otherwise, > the coercion model will not work. > > There should also be some advice in the thematic tutorials. > If you implement with 2 underscores, then you bypass the (generic) coercion implementation. You'd want to implement with a single underscore to ensure common parents (i.e. _richcm_ or _cmp_). Best, Travis -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
