I sent the reply below to Comer earlier, but forgot to cc the list!

Hi Comer,

Yes, it's fine to have xAct loaded when running Kranc. In fact, there is experimental support in Kranc for using xAct as a backend for all of the tensor manipulation that Kranc does. For example, you can set KrancTensor`$KrancTensorNeeds = "xTensorKranc`"; at the start of many of the examples and it should just work (admittedly, I haven't checked it still works with the latest version of Kranc).

In principal, this could be made the default in the future, but right now it is not robust enough. The main problem is that xAct is quite a large, complicated package and it is somewhat overkill for the requirements of Kranc. As a result, there are a few hacks and hardcoded values in Kranc's use of xAct. It may be that the new CTensor features in xCoba would make this worth revisiting, but I don't think anyone has looked at that yet.


Barry

On Wed, Jul 22, 2015 at 4:26 PM, Ian Hinder <ian.hinder@aei.mpg.de> wrote:

On 22 Jul 2015, at 16:04, Comer Duncan <comer.duncan@gmail.com> wrote:

Do Kranc and xAct play well together?  Just curious since sometimes I do things in xAct and then may want to do the same in Kranc and it would be nice if I could just say import xAct and the work done in it to a developing Kranc script.  Of course, there are several pieces of xAct, so maybe my question is not formulated precisely enough, but what do you think?

Hi,

There is experimental support in Kranc for using xAct as an input language.  However, it is not well-tested, and might be missing important functionality.  This was added by Barry Wardell some time ago.  In the past, I have converted xAct expressions into the format expected by Kranc using some simple replacement rules.  Let me know if you would like an example.  Barry might be able to provide more details of the xAct support in Kranc; I'm not sure of the current status.