Hi Jeroen, On 2015-03-04, Jeroen Demeyer <jdeme...@cage.ugent.be> wrote: > On 2015-03-04 14:14, Simon King wrote: >> "Priority" in the sense of "if you want to implement comparison for >> elements, then implement "_cmp_" rather than "__cmp__"? > Yes. In other words: if a Python class has both __cmp__ and _cmp_, the > coercion framework should call _cmp_ (which will default to __cmp__). > > This would make _cmp_ analogous to other operators like _add_. The only > difference is that __cmp__ doesn't inherit if __hash__ is defined, so > you might need to define both __cmp__ and _cmp_.
I don't agree with that description. If a Python class has both __cmp__ and _cmp_ (or both __add__ and _add_), then of course __cmp__ (resp. __add__) are called. What *should* be the case (and I guess it is what you mean): If one implements comparison for an element in Python, then one must not override sage.structure.element.Element.__cmp__. Instead, one should implement _cmp_ (which ought to be a cpdef method). But wouldn't we still have the complication for Cython classes, that one has to actually *copy* code from sage.structure.element.Element? If I recall correctly, this is needed in order to create hashable elements (if you override __hash__ then you must also override __cmp__). That said, this could be resolved in the same way: We should *never* override sage.structure.element.Element.__hash__. Instead, the generic __hash__ method should call _hash_. By consequence, it would not be needed any longer to copy the generic code, since neither __hash__ nor __cmp__ would be overridden (only _hash_ and _cmp_ are). Best regards, Simon -- 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.
