[CM] need macro help!

Elijah Stone elronnd at elronnd.net
Wed Sep 8 13:16:40 PDT 2021

On Wed, 8 Sep 2021, Iain Duncan wrote:

> (define (s4m-process-sexp sexp)

It is entirely a point of style, but I think I would rather make a 
'deepmap' helper function.  Untested, but something like:

(define (deepmap f x)
   (if (not (list? x))
     (f x)
     (cons (deepmap f (car x))
           (deepmap f (cdr x)))))

This also has the convenient side effect of allowing you to e.g. avoid the 
contents of quotes.

> I also noticed I could thus dispense with the oneline macro all together now by doing:
> (define (s4m-run-expr sexp-str)
>   (let ((input-sexp (string->sexp sexp-str)))
>     (eval '(eval (s4m-process-sexp input-sexp)))))

The problem with this is that, since the eval runs in the s4m-run-expr's 
environment, you lose the lexical scope of the caller.  It would be nice 
to be able to say (let ((x 5)) (s4m-run-expr "something with x"))

I think you can evaluate things in the calling environment with a bacro, 
but that's hardly simpler than a regular macro.

> (define-macro (s4m-run-sexp-macro sexp)
>   `(eval (s4m-process-sexp ,sexp)))

Can just be:

(define-macro (s4m-run-sexp-macro sexp)
  (s4m-process-sexp sexp))


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