vary of a variable doesn't work

Question

> ex:=A;
A
> vary(_, $ A ->a $);
Traceback (most recent call last):
  File "<console>", line 1, in <module>
RuntimeException: Do not yet know how to vary that expression.

Thanks!

Answer 1

Thanks for reporting this, will fix. It only fails with expressions containing a single term. This works:

ex:= A+B;
vary(_, $ A -> a $);

Comments

Dear Kasper,

I am getting the same error (using the last version of Cadabra on Ubuntu) when vary acts on a zero term ` ex:=0;

vary(_, $A -> a$); `

---

Thanks, now fixed in 2.3.9.6 on github.

Answer 2

I realized that this is a particular case of http://cadabra.science/qa/79/error-in-using-vary

Sorry for the noise.

Comments

Not really, because you say explicitly how A should be varied. The issue in the present thread really is a bug, while the other thread is a feature request.