Hello Marco, Thank you very much for your help. And, yes I will use the support address in the future for this sort of questions. Since GAP is Open Source anyway, is it possible to subscribe to the support-list? These lists usually become the best knowledgebase around, at least for the other software I work with. ( The only thing that's preventing me from reading the GAP source code is the language, C instead Java. Well, Java wasn't around when it all started. )
Although I am still fairly new to GAP I think it's fair to say that the feedback and answers on this list are both excellent and friendly. Isn't that' a rather unique combination in the field? kind regards, nilo de roock 2006/2/26, Marco Costantini <[EMAIL PROTECTED]>: > Dear Nilo de Roock, > > (Warning: > this answer is a draft, and has not yet been discussed with other people > of the GAP Support Group. More detailed information may (or may not) > arrive later. Feel free to write again if you need more help. For any > remark concerning this mail, please do not reply to me, but write to > [EMAIL PROTECTED] .) > > We offer to react as well as we can to questions, requests for help with > problems, or complaints that you may have. However, for the sake of the whole > user community of GAP, we ask you to separate these into two different > categories. > > GAP Support. We would like to deal with those topics that are more or less > local to you, that is, are likely not of interest to most of the other GAP > users by direct correspondence with you. Please send letters about such local > problems and questions also to the address [EMAIL PROTECTED] > > GAP Forum. On the other hand, the GAP Forum should be reserved for > discussions about problems that are likely to interest many of the GAP users. > It would also be welcome if you could occasionally tell other users in the > GAP Forum about interesting applications you have made of GAP. > > > On Sunday 26 February 2006 11:44, Nilo de Roock wrote: > > Hello GAP forum, > > > > Forgive for yet another question (...) on this command, perhaps I am using > > the wrong command for my purpose. When I execute the following command. > > > > gap> List(AllGroups(20),StructureDescription); > > > > GAP responds with > > [ "C5 : C4", "C20", "C5 : C4", "D20", "C10 x C2" ] > > > > The issue I have here is that "C5:C4" occurs twice in the list. > > Yes, in fact StructureDescription is not injective, an two of the groups with > 20 elements have a similar structure. > > > What I am > > looking for is a command that would recognize that the Frobenius group > > <s,t; s^4 = t^5 = 1, ts = st^2> is in there somewhere. > > > > > > Even if I do... > > > > gap> F:=FreeGroup(2); > > <free group on the generators [ f1, f2 ]> > > gap> s:=F.1; > > f1 > > gap> t:=F.2; > > f2 > > gap> G:=F/[s^4,t^5,t*s*t^-2*s^-1]; > > <fp group on the generators [ f1, f2 ]> > > gap> Size(G); > > 20 > > gap> str(G); > > "C5 : C4" > > gap> > > > > the answer is "C5:C4". > > > > > > I am getting lost on this command, and thus on GAP. Please help. > > A possibility is simply > > gap> IdGroup(G); > [ 20, 3 ] > > that is, G is the 3rd group in AllGroups(20) . > > Another possibility is to use StructureDescription only to restrict to some of > the groups, and then to proceed with something else. For instance > > gap> G_20_1 := SmallGroup(20,1); > <pc group of size 20 with 3 generators> > gap> G_20_3 := SmallGroup(20,3); > <pc group of size 20 with 3 generators> > > After using StructureDescription you know that the other groups with 20 > elements are not isomorphic to your G. > > After that you can use: > > gap> IsomorphismGroups( G_20_1, G ); > fail > gap> IsomorphismGroups( G_20_3, G ); > [ f1, f2, f3 ] -> [ f1^5, f1^2, f2 ] > > you can also use: > > gap> Length( ConjugacyClasses( G ) ); > 5 > gap> Length( ConjugacyClasses( G_20_1 ) ); > 8 > gap> Length( ConjugacyClasses( G_20_3 ) ); > 5 > > you can also use anything else analogous. > > All the best, > Marco Costantini > _______________________________________________ Forum mailing list [email protected] http://mail.gap-system.org/mailman/listinfo/forum
