Following on from Nick's point, I cannot imagine that users will want or expect to sort a list of groups except possibly by some criterion provided by the user (e.g. size of the group, or something). But apart from that we need to be able to have a default sorting or more or less anything in Sage so that we can have consistent output where possible and meaningful.
John 2008/5/23 David Joyner <[EMAIL PROTECTED]>: > > I agree with Nick and John. > > On Fri, May 23, 2008 at 12:45 PM, Robert Miller <[EMAIL PROTECTED]> wrote: >> >> Hello, >> >> During the last bug day, I found several tickets related to >> inconsistencies in abelian groups. I think I've fixed the circular >> logic, etc. causing the problems in the patch included in #1284. >> However, there is a difference of opinion on notation that I need to >> ask about here. >> >> Q: Should the output of >> sage: G <= H >> for G and H abelian groups be whether G is a subgroup of H? >> >> I know the answer seems simple, but here's why you might want to >> answer no (William suggested this to me). If you have a list of >> abelian groups L = [G1,...,Gn], and you want to quickly sort it, if >> you do sorted(L), you may not get back what you are expecting, since >> the subgroup ordering on abelian groups isn't linear. >> >> gfurnish proposes the alternative sorted(L, >> cmp=canonical_ab_group_cmp), with G <= H returning whether G is a >> subgroup of H. I think I favor this approach. >> >> The other option is G.is_subgroup(H). >> > >> > > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
