Dear Abdulhakeem, > Please can someone explain the reason why i am having this error; and a > possible solution.
> gap> f:=FreeGroup("a","b"); > gap> a:=f.1; b:=f.2; > gap> rel:=[a^4,b^2,b^-1*a*b*a]; > gap> D8:=f/rel; > gap> SetReducedMultiplication(D8); > gap> A:=AutomorphismGroup(D8); > gap> List(A); [...] > gap> f1:=GroupHomomorphismByImages(D8,D8, [ b, b*a^2, a*b ] -> [ b, b*a^2, > a*b ]); First of all, a and b are not elements of D8, they are elements of f, the free group. So you'd first need to do, after defining D8, a:=D8.1; b:=D8.2; (or, perhaps, other variable names, for clarity, etc) Then, [ b, b*a^2, a*b ] -> [ b, b*a^2, > a*b ] is not valid GAP syntax, and anyway this is not what GroupHomomorphismByImages expects as input; instead f1:=GroupHomomorphismByImages(D8,D8, [ b, b*a^2, a*b ],[ b, b*a^2, a*b ]); will to the job. Hope this helps, Dima _______________________________________________ Forum mailing list Forum@mail.gap-system.org http://mail.gap-system.org/mailman/listinfo/forum