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1 point by nlavine 5679 days ago | link | parent

Ah, I see this. I think I have been thinking of macros differently than you have (and probably wrongly). I suppose lexical scoping for macros would make the most difference in the case where a macro expands to a function call, like this:

  (let x 0  ; call (count) to keep a count of things
    (def count () (set x (+ x 1))))

  ; count-ops: count how many lines of code you run.
  (mac count-ops body
    (if body
        (cons (car body)
              (cons '(count)
                    (count-ops (cdr body))))
        '())

  (def foo ()
    (count-ops ; this count-ops call fails
      (with (count 1 step 2)
         ; do some loopy stuff here
      )))
If that's not a compelling example, pretend that count-ops is inserting an interrupt check between every two lines of code. Why is dynamic scoping better for cases like these?

As for real arguments to macros, yes, I meant something like the CL stuff. You're right, though, that macros modify syntax, and I wasn't thinking about them that way. Two posts up you said that macros are "expanded in place". I think that you were thinking about the effect macros have on the code they're called on, whereas I was thinking about the call to the actual macro procedure, and passing arguments to it.