Dear Forum, > On Jan 15, 2019, at 3:26 PM, Will Chen <oxei...@gmail.com> wrote: > > Dear Forum, > > Suppose I have two groups G, H, and a homomorphism f : G --> H, defined > using "GroupHomomorphismByImages". > > Suppose I know that f is surjective, and that moreover there is a > generating set X of H for which I can provide explicit preimages in G. > > Is there a way of giving GAP this information?
You can use SetIsInjective(map,true) and SetIsSurjective(map,true). You also might want to use PreImagesRepresentative instead of PreImage. Then is f is given on pre-images of X with image set X, and H is finitely presented, GAP should be able to calculate such pre-images for arbitrary elements. All the best, Alexander Hulpke _______________________________________________ Forum mailing list Forum@gap-system.org https://mail.gap-system.org/mailman/listinfo/forum
