Oh, I agree, dynamic scoping and lexical scoping are formally equivalent. For one thing, basic computer architectures are all dynamically scoped, with 2^32 (or whatever) variables, one at each memory address. Also, as you say, you can just pick one dynamic variable and use it to hold the lexical environment as you walk through a program. (Unfortunately, I don't know enough to see what the really cool implications of this are, but I'm sure it has some.)
My question is, why is lexical scoping considered better for functions, but dynamic scoping for macros? And more specifically, are these actually cases where different solutions are better, or is it an artifact of the fact that we don't know how to implement lexically scoped macros very well?
