On Nov 22, 2007, at 10:25 AM, William Stein wrote:
> > On Nov 22, 2007 6:53 AM, David Joyner <[EMAIL PROTECTED]> wrote: > \> On Nov 22, 2007 9:35 AM, David Harvey > <[EMAIL PROTECTED]> wrote: >>> >>> Hi all, >>> >>> I'd like to discuss this abelian group thing a bit further, from the >>> point of view of design issues rather than algorithms. >>> >>> Currently in SAGE the situation appears to be the following. An >>> AbelianGroup represents a (not necessarily finite) abelian group >>> whose structure is *known*; i.e. to even create the group object, >>> you >>> need to specify generators and invariants. In fact, even the parent >>> class Group derives from ParentWithGens, so it seems to be >>> impossible >>> to define a "group" whose generators are unknown. >>> >>> What I want to be able to do is create an object representing an >>> abelian group whose structure is *not* a priori known, i.e. is >>> expensive to compute. This is analogous to, for example, creating a >>> matrix by specifying the entries, and then later on asking for other >>> information like the rank, which is an expensive computation, and is >>> subsequently cached. > > You should make an AbstractAbelianGroup class that derives from > ParentWithBase. Hmmm.... but wouldn't it make more sense for AbelianGroup (i.e. the currently implemented one) to derive from AbstractAbelianGroup? i.e. an AbelianGroup is an AbstractAbelianGroup where we happen to know the structure, and so can implement things like order, exponent etc more efficiently? I guess then you have problems with multiple inheritance, since you want AbelianGroup to inherit from both AbstractAbelianGroup and ParentWithGens, both of which originally come from ParentWithBase. That's most unfortunate. david --~--~---------~--~----~------------~-------~--~----~ 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://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
