Kirby writes -

Perhaps some other Pythoneers tracking this list have some overlap with J as well? Anyone care to opine re J?

My focus being in a sense a subset of yours - math through visualization/graphics programming - J has come into play. Working with a copy of "Fractals Visualization and J" by Clifford A. Reiter http://ww2.lafayette.edu/~reiterc/j/index.html. But have not really had the time, impetus to get into the J learning curve. As much as I agree with your multilanguage approach, I personally feel the need to get to a certain level of depth in a particular language before I can get too much out of comparative language approach. And I still don't feel as competent in Python as I would like to be. So I'm still hacking away on PyGeo in my spare time trying to get deeper into performance related issues - e.g. having a tight event loop that only updates/calculates what is necessary as necessary. Mostly stuff that I am sure would be necessary to focus on in its own way in any language I was working with/in. (Also got off the ground on what I was trying to do with complex number visualization using Visual Complex Analysis by Tristan Needham as guide/ inspiration). But I had brought up J on the list earlier and do see it as a natural extension to your executable symbolic math interest and look forward to following your adventures with it. Art