Terra looks really interesting (Halide is another language along this meta-approach - https://halide-lang.org/). It's too bad it never made it further than being used for a few PhD theses.
I like Terra, and I have played with it, but I have not found a use for it to push me to really explore it. I'd love to hear from anyone using Terra for cool projects. I had watched a talk about MAD-X [0] that I found very interesting, but it is specifically for particle accelerator design in physics [1].
[0] https://mediastream.cern.ch/MediaArchive/Video/Public2/weble...
[1] https://mad.web.cern.ch/mad/