Indeed, as someone who's learning a bit of APL on the side I'd love to have a tool that can "explain" a line of APL on demand, e.g. show the parse tree, name built-in functions and operators, expand trains, possibly name common idioms.
I find the concepts in APL very simple. The difficulty for me is in becoming comfortable reading it. Such a tool would make it quick and easy to confirm one's initially very tentative guesses as to what a line means, and gradually you'd come to depend less on it as you get more confident that your initial understanding is right.
And not that I'd recommend using proprietary software, but something that might be helpful for you regarding naming is that Dyalog APL has a top bar with every character used in modern APL, the name of them, and (I think, I've never actually used the system) an example of how to use them.
Thanks for the link. Yes, I've seen other idiom libraries as well, and what I'd like to see is automatic lookup of those idioms, with a name, and optional further breakdown.
