Printing twice changes the output

[fingolfin]

@jankoboehm just sent me this example, maybe @thofma or @fieker have an idea what's going on:
Consider this input:

R, _ = polynomial_ring(QQ, ["x", "y", "z"]);
Z = abelian_group(0);
Rg, (x, y, z) = grade(R,[Z[1], Z[1], Z[1]]);
F1 = graded_free_module(Rg, [2,2,2]);
F2 = graded_free_module(Rg, [2]);
G = graded_free_module(Rg, [1,1]);
V1 = [y*G[1], (x+y)*G[1]+y*G[2], z*G[2]];
V2 = [z*G[2]+y*G[1]];
a1 = hom(F1, G, V1);
a2 = hom(F2, G, V2);
M = subquotient(a1,a2);
m = x*y*z*M[1]

Then we can proceed:

julia> degree(m)
Element of
GrpAb: Z
with components [5]

julia> degree(m)
Element of Z with components [5]

Note that the output changes the second time around.

The problem goes away if I let Z print itself once (e.g. by removing the semicolon at the end of the second line of the initial input).

So my guess is that printing degree(m) somehow leads to the abelian group Z "learning" its name, and then the next time degree(m) is printed, a different path is taken.

Clearly it would be preferable if we get the same printing output in both cases...

@jankoboehm ... but at least the above maybe suggests a temporary workaround for you?

[jankoboehm]

Thanks a lot, did not notice that, it is a good workaround for the moment.

The problem seems not to happen in similar situations, e.g., for polynomial rings. However there is also a (related or unrelated) issue with compact printing, which works in the graded case, but not in the ungraded case.

julia> R, (x, y, z) = polynomial_ring(QQ, ["x", "y", "z"]);
julia> Z = abelian_group(0);
julia> Rg, (a, b, c) = grade(R,[Z[1], Z[1], Z[1]]);
julia> io_compact = IOContext(stdout, :compact => true);

julia> print(io_compact, R)
Multivariate polynomial ring in 3 variables over QQ

julia> print(io_compact, Rg)
Rg

[fieker]

Fixed in Hecke#1106