> It seems to lack data structures that are quite pervasive in modern programming practise.

At least it has multi-dimensional arrays of floats, that is all I need and are sorely lacking in Python. On the other hand, Python has dictionaries and strings, but those are completely useless in a numerical setting.

I agree that the M language is not a good general-purpose programming language. But for expressing linear algebra manipulations is probably the best in town.