[avmich]

One of core things (ideas, requirements) in APL is to make mathematical notation in one line.

Another thing (restriction) was to use available hardware. So some symbols were created in a way which was possible to achieve with teletypes of the days.

It's possible one should start with careful (re-)reading of "A programming language".

And maybe we should think once again about the power of the whiteboard and how we could express that into an executable language.

[robomartin]

Right! Some of the characters were over-types! The teletype would print one standard character, advance to to the next position, then backup to the character it just printed and over-print it with a second. The quote-quad is an example of this. It would print a quote and then backup and print a rectangle standard drawing character over it.