about summing different indices and outputs

Question

Hi, I have a question about Cadabrav2 and v1. When I set position=fixed in indices properties , I was expecting an error to occur when writing things as follows:

{a,b,c}::Indices(position=fixed);
exp:=A_{b} A_{b} + A_{b} A^{b};

But this gives as output the same line : $A_{b} A_{b} + A_{b} A^{b}$. In Cadabra v1 the same story goes.

Moreover, i put in Cadabrav2

{a,b,c}::Indices(position=fixed);
exp:=A_{b} A_{b} + A_{b} A^{b} + B_{a};

And the output was fine again, no error!. In Cadabra v1 the output tells you that the indices of different terms do not match.

So the questions are: how can you tell the effect of position=fixed either in Cadabra1 or 2 (or to let you know that Einstein convetion on contravariant and covariant indies is being violated) and second question is: where are the error outputs from Cadabrav2 ? (One more thing, in cadabrav1 when you apply an algorithm until no longer changes it will let you know, but cadabrav2 does not say anything about a repetitive algorithm action or at least i dont know how to see it).

I really appreaciate the effort in trying a second version for Cadabra. But for the time being, I will keep using Cadabra v1 since it has more algorithms and it runs much more faster than Cadabra v2 (at least this happens in my computer).

thank you very much,

Answer 1

Thanks for reporting this. The index consistency checker was disabled on new input lines a while ago, and I forgot to turn it back on... Will fix, and then v2 should report all the things wrong with the expressions you listed.

Concerning missing algorithms: please do let me know which things you miss most. And also let me know which things run much slower in v2.

Answer 2

The version now on github fixes all of these (for v2, that is):

{m,n}::Indices(position=fixed);
ex1:= A_{m} A_{m};
ex2:= A_{m n} + A_{m};
ex3:= A_{m n} A^{m} B_{m};

now all throw an error. Hope this helps.