[sage-devel] Re: Bug in hom

2020-12-29 Thread 'Travis Scrimshaw' via sage-devel
If we just fix the bug in the corresponding Homspace's __call__method to make sure the domains match by pre/postcomposing using the appropriate coercion maps when the objects are equal-but-not-identical, then it will fix the problem because things would be described in terms of the same basis.

[sage-devel] Re: Bug in hom

2020-12-27 Thread enriqu...@gmail.com
Dear Travis, I basically agree with you, in the sense to fix that what equality means. At this time, equality of vector spaces does not imply equality of associated vectors. I think both choices have good reasons. I am not sure how to collaborate with these issues but I am ready to. Best, Enriqu

[sage-devel] Re: Bug in hom

2020-12-26 Thread 'Travis Scrimshaw' via sage-devel
We need to be very careful here about what "same" means, and the category we want to work in is vector spaces with a distinguished basis. By similar I really meant up to a change-of-basis, and I should have been more precise. Although perhaps it is a more simple problem than I was thinking beca

[sage-devel] Re: Bug in hom

2020-12-24 Thread enriqu...@gmail.com
Not exactly, when one asks if two linear maps are equal it is not the same thing to ask if they are similar, I mean equal as maps. In my example, if you enter: K=GF(2) V=K^2 B=V.basis() B1=[vector(K,[i,j]) for i,j in [(1,0),(1,1)]] V1=V.subspace_with_basis(B1) and you ask V==V1 the answer is T

[sage-devel] Re: Bug in hom

2020-12-23 Thread 'Travis Scrimshaw' via sage-devel
What you're asking for is checking if two matrices defining the linear transformations are similar, which involves computing the Smith normal forms of the matrices. This is computationally expensive. Instead, what we do is == becomes a weaker form of equality that is fast (equivalently has stro