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by lispm 3552 days ago
That's not too far away from Lisp. But in Lisp we would be using some quasiquote templates for this simple macro:

    (defmacro debug-it (&body expressions)
      `(progn
         ,@(mapcar (lambda (expression)
                     `(format t "~%~a: ~a" ',expression ,expression))
                   expressions)))
Example:

    CL-USER 8 > (pprint (macroexpand-1 '(debug-it (+ 1 2) (* 3 4))))

    (PROGN
      (FORMAT T "~%~a: ~a" '(+ 1 2) (+ 1 2))
      (FORMAT T "~%~a: ~a" '(* 3 4) (* 3 4)))

    CL-USER 9 > (debug-it (+ 1 2) (* 3 4))

    (+ 1 2): 3
    (* 3 4): 12
    NIL
1 comments

I could have done that, but I couldn't be bothered to look up the interpolation strings for format (yes, we have it), or the one level flatten function, and the splicing unquote is less efficient than cons in this case. But yes, in real code, I'd probably go in that direction.

There is one key difference between my code and yours: in mine, the functions, values, and symbols referenced in the macro are automatically renamed, thus guaranteeing no namespacing conflicts. Due to the way the CL package system works (IIRC), CL provides almost the same guarantees, at least in this case. But it is an important semantic difference.

And it is the Common Lisp. Despite how you may feel, Scheme, Clojure, PicoLisp, NewLisp, Racket, Interlisp, LeLisp, EuLisp, and others are as much a Lisp as CL.

Procedural macros were introduced to Lisp twenty years before CL existed and quasiquotation around ten years before CL existed.

> and the splicing unquote is less efficient than cons in this case

Not sure why that should be the case and why it even matters.

True, but as my code aptly demonstrated, procedural macros don't work the same jb all Lisps. Some Lisps don't even have them.

AFAICT, splicing unquote has to traverse the entire result list. Not super relevant in this case.

I don't know why I picked cons, honestly. I guess it just fit ny mental model of what was happening better.

> AFAICT, splicing unquote has to traverse the entire result list. Not super relevant in this case.

Especially since it is usually done once at compile time.

> Some Lisps don't even have them.

Even most Scheme implementations have them.

Well, then it's slowing down compilation.

And yes, most schemes have them. I was talking about Picolisp, Newlisp, and Kernel, which don't.

> Well, then it's slowing down compilation.

My five MIPS Lisp Machine did not care. My Lisp implementations on a several hundred times faster processor don't care either.

These languages you list don't have macros.