[GAP Forum] Failed to run AreRepsIsomorphic command.

[Hongyi Zhao]

On Sat, Apr 30, 2022 at 4:38 PM Dima Pasechnik <dima at sagemath.org> wrote:
>
> On Sat, Apr 30, 2022 at 08:14:15AM +0800, Hongyi Zhao wrote:
> > Hi GAP team,
> >
> > Based on the guidance here [1], I tried to do the following testing but failed:
> >
> > gap> LoadPackage("RepnDecomp");
> > true
> > gap> g:=CyclicGroup(IsFpGroup,8);
> > <fp group of size 8 on the generators [ a ]>
> > gap> AreRepsIsomorphic(IrreducibleRepresentations(g),IrreducibleRepresentations(SmallGroup(8,1)));
> > Error, no method found! For debugging hints type ?Recovery from NoMethodFound
> > Error, no 1st choice method found for `Source' on 1 arguments at
> > /home/werner/Public/repo/github.com/gap-system/gap.git/lib/methsel2.g:249
> > called from
> > Source( rep1
> >  ) at /home/werner/Public/repo/github.com/gap-system/gap.git/pkg/repndecomp/lib/isomorphism.\
> > gi:234 called from
> > <function "AreRepsIsomorphic">( <arguments> )
> >  called from read-eval loop at *stdin*:18
> > type 'quit;' to quit to outer loop
> >
> >
> > How to fix the above command?
>
> AreRepsIsomorphic does not take lists of representations as arguments, it takes individual
> representations.
>
> It is meant to be used on representations with the same underlying group, in your setting it might not work
> (say, because different generators are used).

I still don't know how to use it. Please see my example below:

gap> LoadPackage("RepnDecomp");
true
gap> g:=CyclicGroup(IsFpGroup,8);
<fp group of size 8 on the generators [ a ]>
gap> AreRepsIsomorphic(IrreducibleRepresentations(g));
Error, Function: number of arguments must be 2 (not 1)
not in any function at *stdin*:12
type 'quit;' to quit to outer loop

> HTH
> Dima