Testing membership in an (known to be) inverse RZMS can fail

Issue #126 resolved
wilfwilson
created an issue

Testing membership of this element is fine before doing IsInverseSemigroup, but it fails afterwards:

gap> mat := [
> [ (), 0, 0, 0, 0 ],
> [ 0, (3,4), 0, 0, 0 ],
> [ 0, 0, (), 0, 0 ],
> [ 0, 0, 0, (1,2), 0 ],
> [ 0, 0, 0, 0, (1,2)(3,4) ] ];;
gap> R := ReesZeroMatrixSemigroup(Group([ (1,2), (3,4) ]), mat);;
gap> gens := [
> MultiplicativeZero(R),
> RMSElement(R, 4, (), 4),
> RMSElement(R, 4, (1,2)(3,4), 4),
> RMSElement(R, 5, (1,2)(3,4), 5),
> RMSElement(R, 5, (1,2), 5),
> RMSElement(R, 4, (1,2), 4),
> RMSElement(R, 1, (1,2), 1),
> RMSElement(R, 1, (3,4), 1),
> RMSElement(R, 2, (3,4), 2),
> RMSElement(R, 2, (1,2), 2),
> RMSElement(R, 1, (1,2), 1),
> RMSElement(R, 3, (), 3),
> RMSElement(R, 3, (1,2), 3),
> RMSElement(R, 1, (1,2), 1) ];;
gap> U := Semigroup(gens);;
gap> Filtered(R, x -> x in U);;
gap> x := RMSElement(R, 1, (), 2);;
gap> x in U;
false
gap> IsInverseSemigroup(U);
true
gap> x in U;
Error, List Element: <list>[6] must have an assigned value in
  x := gens[genpos[1][i]] * trace( genpos[2][i] ); called from 
trace( i ); called from
RhoOrbMult( RhoOrb( S ), n, pos_rho ) called from
<function "unknown">( <arguments> )
 called from read-eval loop at line 28 of *stdin*

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