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gap-packages / polycyclic

Computation with polycyclic groups
https://gap-packages.github.io/polycyclic/
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TorsionSubgroup returning wrong results for abelian groups #52

Open fingolfin opened 3 years ago

fingolfin commented 3 years ago

Reported by Matthias Neumann-Brosig via email:

gap> # Using Gap 4.11.0 with Polycyclic 2.15.1
gap> G := AbelianPcpGroup([3,2,0,0]);
Pcp-group with orders [ 3, 2, 0, 0 ]
gap> TorsionSubgroup(G);
Pcp-group with orders [ 3 ]
gap> G := AbelianPcpGroup([2,3,0,0]);
Pcp-group with orders [ 2, 3, 0, 0 ]
gap> TorsionSubgroup(G);
Pcp-group with orders [ 2, 3 ]
fingolfin commented 3 years ago

My guess is that #51 will help with it, but we'll see

stertooy commented 3 years ago

I'm not getting this error in version 2.16. I suspect this is the same bug I reported to @beick in early 2020, which was fixed in 901f1a5ae52754d4e6399c4609bce98be8c3db18. A testcase for this bug was added in e7d428cb42ed9b2682e31ef675d6fb13e05d1aed, it seems.