[GAP Forum] Strange GAP, II

[Alexander Hulpke]

Dear Forum,

Anvita21 asked
> 
> If a pcgs has an element "g" of infinite relative order,
> the negative exponents of "g" seem to hang the function
> "ExponentsOfPcElement". For example, the program
> 
> -------------------------------------------
> F:=FreeGroup(1);
> g:=F.1;
> p := PcgsByPcSequence( FamilyObj(g), [g] );
> ExponentsOfPcElement(p,g^-1);
> -------------------------------------------
> 
> instead of returning -1 runs forever.
> It this the expected behavior?

Yes, as the implementation of pcgs in the library assumes that the group is finite. The `Polycyclic' package allows infinite polycyclic groups and their polycyclic generating systems, but they need to be represented suitably, on cannot simply take a free group.

Best,

    Alexander Hulpke



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