[markvangulik]

As for SHRDLU, it was built atop a “language”, PROGRAMMAR, if I recall, which was really a big ball of Lisp, so the syntax was basically tons of parentheses with keywords inside the left one. But given the available languages, memory, and speed of that time, it was amazing that even a library-ish extension of Lisp could come into play.

Note that embedding PROGRAMMAR inside Lisp is exactly the kind of thing we’re doing with Avail… it’s just that the base metarules are more articulate for that sort of thing.

PROGRAMMAR rewritten today in Avail wouldn’t look at all like Lisp — thank goodness. But if you implemented that language via a compiler, you would have the limitations of the compiler technology constantly getting in the way of the linguistic forms you’re trying to express. For example, having to decide on a linear ranking of precedence levels for every operation, even if they couldn’t ever appear next to each other due to type or linguistic constraints.

Even C++ requires custom lexing tweaks because of spurious “>>” tokens in nested templates… and special backtracking rules to distinguish function definitions from stack object creation. But those bypasses aren’t readily usable in the available parsing tools. Avail’s compiling scheme is decades beyond that.