I agree, any reference to 1 should fail. But does the zero element of an algebra (i.e. its neutral element as a Z-module) really have to refer to the identity element of the algebra? Also, it probably should throw an error, instead of getting stuck in an infinite loop.
Best, Akos On Friday, February 4, 2022 at 1:17:33 AM UTC+1 Travis Scrimshaw wrote: > As I stated on the ticket, this is not a bug because you have not properly > defined your algebra. It needs to have an (multiplicative) identity > specified as it is rightfully expecting it. This is the correct behavior > because you are saying it is an algebra without specifying what the algebra > structure is. In particular, you need to specify what one() is. > > Best, > Travis > > On Friday, February 4, 2022 at 7:49:19 AM UTC+9 vdelecroix wrote: > >> There is an explanation and a "solution" on the ticket. >> >> Best >> Vincent >> >> Le 03/02/2022 à 23:48, Akos M a écrit : >> > Replacing 0 with self.zero() works perfectly, thank you! >> > >> > Best, >> > Akos >> > >> > On Thursday, February 3, 2022 at 11:34:43 PM UTC+1 Akos M wrote: >> > >> >> Thanks for the feedback. >> >> >> >> Indeed, defined as such, C is a broken object - this was just the >> smallest >> >> example where I could reproduce the error. >> >> >> >> I was hoping that it should be possible to access the module elements >> >> without referring to 1, or multiplication. >> >> I would like to define multiplication later in the definition of some >> >> algebraic structure, but still inherit the methods from the category. >> >> (Similarly to >> >> >> https://doc.sagemath.org/html/en/thematic_tutorials/coercion_and_categories.html >> >> >> ) >> >> >> >> In particular, the error originally appeared in the form of >> >> "if x == 0:" >> >> where x is an element of the module, as should be 0 (now coerced..). >> >> >> >> Best, >> >> Akos >> >> On Thursday, February 3, 2022 at 10:10:29 PM UTC+1 vdelecroix wrote: >> >> >> >>> Now I am thinking about it, I am not sure it is a bug. You did >> >>> not defined any algebra structure (neither the unit nor the >> >>> product on the basis). C is definitely a broken object. >> >>> >> >>> However, it would make sense for C(0) not to call C(1). >> >>> >> >>> Vincent >> >>> >> >>> Le 03/02/2022 à 21:49, Akos M a écrit : >> >>>> Thanks, I created - my first - ticket. >> >>>> https://trac.sagemath.org/ticket/33285#ticket >> >>>> >> >>>> Once the ticket is (eventually) resolved, how do I update sage to >> >>> involve >> >>>> the resolution? >> >>>> >> >>>> Thanks, >> >>>> Akos >> >>>> >> >>>> On Thursday, February 3, 2022 at 1:39:10 PM UTC+1 vdelecroix wrote: >> >>>> >> >>>>> It is definitely a bug. Do you know how to open >> >>>>> a ticket on the trac server ? >> >>>>> >> >>>>> The infinite loop comes from C.one() calling C(1) >> >>>>> calling C.one()... When you specify a category >> >>>>> the inheritance is different and this explains >> >>>>> the difference of behaviour. >> >>>>> >> >>>>> Best >> >>>>> Vincent >> >>>>> >> >>>>> Le 03/02/2022 à 11:29, Akos M a écrit : >> >>>>>> >> >>>>>> >> >>>>>> Hi, >> >>>>>> >> >>>>>> The snippet >> >>>>>> D = CombinatorialFreeModule(ZZ, [1,2]) D(0) >> >>>>>> >> >>>>>> works fine, however >> >>>>>> C = CombinatorialFreeModule(ZZ, [1,2], >> >>> category=AlgebrasWithBasis(ZZ)) >> >>>>> C(0) >> >>>>>> >> >>>>>> gets into an infinite loop: >> >>>>>> File >> >>>>>> >> >>>>> >> >>> >> "/opt/sagemath-9.0/local/lib/python3.7/site-packages/sage/categories/magmas.py", >> >> >> >>> >> >>>>>> line 488, in one return self(1) File "sage/structure/parent.pyx", >> >>> line >> >>>>> 900, >> >>>>>> in sage.structure.parent.Parent.__call__ >> >>>>>> (build/cythonized/sage/structure/parent.c:9218) return >> mor._call_(x) >> >>> File >> >>>>>> "sage/categories/map.pyx", line 1694, in >> >>>>>> sage.categories.map.FormalCompositeMap._call_ >> >>>>>> (build/cythonized/sage/categories/map.c:11607) x = f._call_(x) >> File >> >>>>>> "sage/categories/morphism.pyx", line 549, in >> >>>>>> sage.categories.morphism.SetMorphism._call_ >> >>>>>> (build/cythonized/sage/categories/morphism.c:8489) cpdef Element >> >>>>>> _call_(self, x): File "sage/categories/morphism.pyx", line 568, in >> >>>>>> sage.categories.morphism.SetMorphism._call_ >> >>>>>> (build/cythonized/sage/categories/morphism.c:8439) return >> >>>>> self._function(x) >> >>>>>> File >> >>>>>> >> >>>>> >> >>> >> "/opt/sagemath-9.0/local/lib/python3.7/site-packages/sage/categories/unital_algebras.py", >> >> >> >>> >> >>>>>> line 70, in from_base_ring return self.one()._lmul_(r) File >> >>>>>> "sage/misc/cachefunc.pyx", line 2310, in >> >>>>>> sage.misc.cachefunc.CachedMethodCallerNoArgs.__call__ >> >>>>>> (build/cythonized/sage/misc/cachefunc.c:12712) self.cache = >> >>>>>> f(self._instance) >> >>>>>> >> >>>>>> Why is this? Is this expected behaviour? >> >>>>>> (Also asked on: >> >>>>>> >> >>>>> >> >>> >> https://ask.sagemath.org/question/60903/possible-bug-specifying-category-messes-up-coercion/ >> >> >>>>> ) >> >>>>>> >> >>>>>> Thanks, >> >>>>>> Akos >> >>>>>> >> >>>>> >> >>>> >> >>> >> >> >> > >> > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/2d426aef-78ce-4cd8-b170-b7fa46e3a3e5n%40googlegroups.com.
