On Friday, February 14, 2014 9:06:35 PM UTC-8, John H Palmieri wrote: > > > > On Friday, February 14, 2014 6:18:42 PM UTC-8, Mark Shimozono wrote: >> >> Nicolas, >> >> > In your case, to implement the smash product, you probably want to >> > implement a subclass of CombinatorialFreeModuleTensor, set its >> > category to the join of ModulesWithBasis(QQ).TensorProducts() and >> > AlgebrasWithBasis(QQ), and implement the product similarly to what's >> > done for tensor products of algebras with basis. >> >> I would dearly love to be able to construct elements in my class in an >> automatically multilinear way, using the _tensor_of_elements method >> for tensor products of modules. However sage won't let me. >> Basically it has an overly restrictive type check which fails. >> >> Here is a toy version of my class: >> >> class MyTensorProductOfAlgebras(CombinatorialFreeModule_Tensor): >> def __init__(self, A, B): >> R = A.base_ring() >> CombinatorialFreeModule_Tensor.__init__(self, [A,B], \ >> category=Category.join((AlgebrasWithBasis(R),ModulesWithBasis(R).TensorProducts()))) >> >> >> >> The code calling the _element_tensor method for the >> vanilla instance T: >> >> sage: L = CartanType(['A',2]).root_system().weight_lattice() >> sage: A = L.algebra(ZZ) >> sage: a = A.an_element() >> sage: T = tensor([A,A]) >> sage: T._tensor_of_elements([a,a]) >> B[2*Lambda[1] + 2*Lambda[2]] # B[2*Lambda[1] + 2*Lambda[2]] >> >> and the custom class TT: >> >> sage: TT = MyTensorProductOfAlgebras(A,A) >> TT._tensor_of_elements([a,a]) >> >> AssertionError >> >> and the offending line is: >> >> assert(sage.categories.tensor.tensor(modules) == self) >> >> where "modules" is the list of modules to be tensored and "self" >> is the instance that is invoking _tensor_of_elements. >> >> Note that >> >> sage: T >> >> and >> >> sage: TT >> >> give the same exact description string. >> >> Any solutions/workarounds? Surely there is no need to reimplement the >> multilinearity! >> >> --Mark >> > > You could reimplement the 'tensor_constructor' method for your class: just > copy over the one from CombinatorialFreeModule_Tensor in > combinat/free_module.py, but delete the line > > assert(sage.categories.tensor.tensor(modules) == self) > > Or you could patch free_module.py, adding an optional argument, say > "type_check=True", to both tensor_constructor and _tensor_of_elements, and > only do this assertion if type_check is True. >
Oh, heh, if you go this route, then you actually have to use the optional argument somehow. Maybe instead you should define an attribute self._type_check and set it when you initialize an instance of the class. The default value would be True, but when you initialize your version, you would set it to False. -- John > -- You received this message because you are subscribed to the Google Groups "sage-combinat-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-combinat-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-combinat-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-combinat-devel. For more options, visit https://groups.google.com/groups/opt_out.
