[srean]

Yes am familiar with Eigen. And yes I am/was that lunatic you mention in your other comment.

This thing I wrote, predated Eigen (by a few years, I think) had a better support for pipelines and dataflow oriented programming (at least in the context of what I needed) than Eigen. It was more like itertools, functools of Python. Likely older than Eigen but positively after Blitz++ because I remember studying Blitz++ code.

Unlike Eigen, mine had no explicit support for intrinsics, for that I relied on a smart enough compiler, GCC was surprisingly good.

Too bad MSVC was quite bad at optimising and inlining away to the expression trees that Eigen (and mine) generated.