Cool, but I was disappointed to find that it assumes you already know enough APL to understand the extensional definitions or analogies it gives. I was hoping it would be more of a “bootstrapping APL from a simple, explicitly-defined-in-the-text set of operators” kind of thing.
APL is not so much a model of computation as a new notation for semantics which already exist. The real semantic explanation of APL is set theory and traditional mathematics.
Probably the best deep ground-level explanation of APL is Iverson’s paper “Notation as a tool of thought.” [0]
The bootstrapping explanation you describe sounds a lot like what Paul Graham did in “On Lisp” [1] and in a much more complex fashion, Queinnec in “Lisp in Small Pieces” [2], both highly recommended.
