[plt-scheme] Struggling with macro...

Paulo J. Matos wrote:
>  (define-syntax (machine stx)
>    (syntax-case stx ()
>      [(_ mname sexps ...)
>       (identifier? #'mname) ; fender
>       #'(let ([mc (make-mc () () () () ())])
>           #,(with-syntax ([variables (syntax-case #'(sexps ...) (variables)
>                                        ((variables (name value) ...)
>                                         (andmap identifier? #'(name ...))
>                                         ((add-variable-to-mc #'name
> #'value) ...)))])
>               #'variables
>               #'mc))]))
> 
> This gives me: syntax: no pattern variables before ellipses in template 
> in: ...

The first problem is the #' before the let.  Since you are using #, 
(unquote-syntax) then you need #` (or quasisyntax), not #' (or syntax). 
  In other words, it must be:

#`(let ([mc .....

Another problem is that in the inner syntax case #'(sexps ...) actually 
starts as:

((variables (x 1)

not

(variables (x 1)

So, it won't match the one clause in the syntax-case.  One way to help 
see this is to add lines like this to your macro, to run at transform 
time, not runtime.

(printf "(sexps ...) = ~a~n" (syntax-object->datum (syntax (sexps ...))))

Here is something that works, but it may not fit your real situation:

(define-syntax (machine stx)
   (syntax-case stx (variables)
     [(_ mname (variables (name value) ...))
      (identifier? #'mname) ; fender
      #'(let ([mc (make-mc () () () () ())])
        	  (add-variable-to-mc name value) ...
           mc)]))


Rob