[luatex] macros to invoke lua in LaTeX

[Karl Berry]

    Which nicely demonstrates that LaTeX was designed with a completely
    frozen engine in mind

I agree with that statement.  But lacking a time machine, the situation
is what it is: it is not reasonable to ignore the fact that much of the
world's mathematics over the past two decades has been written in LaTeX,
i.e., expect the world to adjust to us.  That would not happen.  What
would happen is that luatex would not be used except by a few hard-core
devotees.  That is not a desirable outcome from my point of view.