What is the sensible notion of parent() for a vector that I drew out of a vector subspace? For instance, what should be printed by the following lines?
VS = (QQ^3).subspace([ (1, 1 ,1) ]) v = VS.an_element() print v.parent() One possibility is that QQ^3 should be printed. Alternatively, and the current behaviour of Sage, is to return the vector subspace VS as the parent. This surprises me at least. I think of parent() vaguely in the general sense of type (not Python's primitive notion of type, of course, but a more advanced type system). By that logic, I would say that the vector v above is foremost of the "type" QQ^3 element. It also happens to be in many vector subspaces of QQ^3 but that doesn't matter. But there might be a bigger picture I'm not seeing here. What do people say? [ ]: Vectors drawn from a subspace have that subspace as parent. [ ]: Vectors over R^n should have R^n as parent, no matter where they "came from". This relates to the thread https://groups.google.com/forum/#!topic/sage-devel/rvs5E6AEXVc and to what should be patched to avoid the surprising behaviour mentioned there. More precisely, if the current parent-behaviour should be retained, a check should be introduced when modifying copies of vectors from VS. If the parent-behaviour is changed, however, no other patch is necessary. Best, Johan -- 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.
