explicit_indices used in two trace

Question

In fact, there are two questions. First, for example,

{a,b,c,d}::Indices(vector).
tr{#}::Trace.
A::ImplicitIndex(A_{a b}).
B::ImplicitIndex(B_{a b}).
ex:=tr(c A B) tr(A B);
untrace(_);
explicit_indices(_);

A,B are not ImplicitIndex, is it a bug? Second, I rewrite the above code using

{a,b,c,d}::Indices(vector).
tr{#}::Trace.
{A,B}::ImplicitIndex.
ex:=tr(c A B) tr(A B);
untrace(_);
A::ImplicitIndex(A_{a b}).
B::ImplicitIndex(B_{a b}).
explicit_indices(_);

but it doesn't work. The error report is

{RuntimeError: Double index pair a inside a single factor found.

At:
  <string>(9): <module>

Is this another bug?

Answer 1

The first problem arises because you did not tell tr over which indices it traces. If you have ImplicitIndex objects inside the trace which have an explicit form listed, then you also need to specify the indices on which tr acts, otherwise it takes those objects out. Perhaps the default is not entirely logical, apologies. So this is easily fixed by using

tr{#}::Trace(indices=vector).

instead.

The second problem was a bug, thanks for reporting it. It is now fixed on github with version 2.3.5.4.

Comments

Thanks for your labor. By the way, the question https://cadabra.science/qa/1868/only-one-window-can-be-opened is still unsolved, and I have tried all methods I can consider, including reinstalling the Ubuntu system. Can you give me some further suggestions?