gap> Q:=QuadraticNumberField(-2);;
gap> OQ:=RingOfIntegers(Q);;
gap> I:=QuadraticIdeal(OQ,4+9*Sqrt(-2));;
gap> G:=HAP_CongruenceSubgroupGamma0(I);;
gap> R:=ResolutionSL2QuadraticIntegers(-2,4,true);;
gap> S:=ResolutionFiniteSubgroup(R,G);;
gap> C:=TensorWithIntegers(S);;
gap> D:=ContractedComplex(C);;
gap> C!.dimension(2); C!.dimension(3);
1620
1620
gap> D!.dimension(2); D!.dimension(3);
49
50
gap> Homology(D,2);
[ 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 0, 0, 0 ]
