Missing labels after + and -

[chiamin]

In A=B+C, the label of A will be reset to ['0','1',...] regardless of the labels of B and C. Is this the correct behavior we want? I propose that we should require the labels to be the same for B and C, and set the same labels for A.

Here is a minimal example.
bug_report_label_arithmetic.py

[pcchen]

I don't think it is necessary to require labels to be the same for B and C.
User can decide if they want/need to copy the labels from B or C.

[chiamin]

Then it is a matter of design. (I have changed the label to suggestion.) It depends on how much we want to emphasize using a label to represent an index. If we use labels to represent indices, it is natural to expect that we add tensors that share the same labels (assuming, but not guaranteeing, they are matched) and return a tensor with the same labels. If we don't require A and B to have the same labels, we cannot assign the labels to C=A+B (which is the current design). The current design is a bit confusing to me, but I can live with that.

[chiamin]

If @pcchen or @yingjerkao decides to keep the current design, I will close this issue.