How to make a vector of parametric composite types?

OK, I’ll try be quick. First, “lispy recursion” is demonstrated by the pattern here: 0.6: how do you broadcast `call` over a vector of functions? - #12 by andyferris. (Note the timing differences with/without type stability in that thread.)

It uses an @inline function and splatting ... to cleverly build up, piece by piece, each answer to f(x) into a tuple.