On Wed, May 30, 2018 at 8:14 AM, Travis Scrimshaw <tsc...@ucdavis.edu> wrote: > > > On Tuesday, May 29, 2018 at 9:01:51 PM UTC+10, chris wuthrich wrote: >> >> >> As a simple-minded user I stumbled over exactly this last week. I don't >> understand much of what this thread is discussing, but I know what a >> simple-minded user wants. >> >> sage: G = GL(2,13) >> sage: G = G.as_matrix_group() >> sage: H = G.subgroup([ matrix(GF(13),[[1,0],[1,1]]) ]) >> sage: H2 = G.subgroup([ matrix(GF(13),[[1,1],[0,1]]) ]) >> sage: H3 = G.subgroup([ matrix(GF(13),[[1,0],[2,1]]) ]) >> >> I expect H == H3 to say True as they are the same subgroup. >> I expect H = H2 to say False, since they are not the same subgroup, even >> though they are isomorphic. >> Instead >> >> sage: H == H3 >> False >> sage: matrix(GF(13),[[1,0],[1,1]]) in H3 >> True >> sage: matrix(GF(13),[[1,0],[2,1]]) in H >> True >> sage: H.is_isomorphic(H3) >> True >> sage: H.is_isomorphic(H2) >> True >> sage: matrix(GF(13),[[1,0],[1,1]]) in H2 >> False >> >> I though of working around it by checking if they are the same as sets, >> but to my surprise: >> >> sage: Set( h for h in H ) == Set( h for h in H3 ) >> False >> sage: Set( h.matrix() for h in H ) == Set( h.matrix() for h in H3 ) >> True >> >> In short: I consider this a bug. No matter how this is done at the back, >> the user expects == to mean mathematical equality, here equality of >> subgroups. Otherwise the function should be called >> subgroups_with_given_generators.
"mathematical equality" is also a red herring being that there are many possible definitions thereof. Are we talking equality up to isomorphism? Etc... -- 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 https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
