On Wednesday, June 3, 2015 at 11:02:42 PM UTC+2, David Roe wrote: > > > For a vector space V over an inexact field, the statement that a vector v > belongs to a particular subspace W cannot be checked by examining an > approximation to v in V. For example, (2 + O(3^50), 4 + O(3^50)) may or > may not be in the span of (1 + O(3^50), 2 + O(3^50)). A better way to > record the precision of v is by a lattice inside W. In the above example, > you could just say that the x-coordinate has uncertainty O(3^50) and that v > lies in the span of (1,2). In order to enable this, you really want to be > able to set W as v's parent. There are plenty of ways to get a vector in V > if this isn't the behavior you want. > > > I don't think I understand what you're saying. If I do the following in Sage:
R = pAdicField(3) V = R^2 W = V.subspace([vector(R, [R(1), R(2)])]) v = vector(R, ( R(2), R(4) )) print v in W print v.parent()== W it prints True False So v is considered a vector in W even though it doesn't have W as parent. Thus, when it comes to determining subspace membership we don't need to set the parent of W's vectors to W in order to retain the current behaviour. Or there's something I'm not understanding? 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.
