My thought here is that a, b, c, d are expression placeholders (and assuming they don't contain commas in the ALGOL syntax version). It's (print a b c d) if all

My thought here is that a, b, c, d are expression placeholders (and assuming they don't contain commas in the ALGOL syntax version). It's (print a b c d) if all arguments to the ALGOL version are already terminal symbols. If instead it was print(foo.a, foo.b, foo.c, x + y) it's now (print (get-a foo) (get-b foo) (get-c foo) (+ x y)).