Expanding Macros

[Thomas Del Vecchio]

I'm trying to work through expanding a macro to pass the result into another macro. I've attached and pasted the spec below that is my toy example. I've tried using expand, but it gives me "(C (#%app (#%top . B) (quote 1) (quote 2)))" instead of "(C (in 1 2))". I've also tried many other things, but none seem to do what I expect/want. Any help?

#lang racket

(require (for-syntax syntax/parse))

 

; I want A to take a (B x y) expand it to be passed to C.

; (A (B 1 2))

; -> (C (in 1 2))

(define-syntax (A stx)

  (syntax-case stx (A)

    [(A b)

     (with-syntax ([expanded-b #'b]) ; <- what goes here?

     #'(C expanded-b))]))

 

(define-syntax (B stx)

  (syntax-case stx (B)

    [(B x y)

     #'(in x y)]))

 

(define-syntax (C stx)

  (syntax-case stx (C in)

    [(C (in x y))

     #'(printf "~a ~a ~n" x y)]))

 

(A (B 1 2)) ; expect to print "1 2 ~n"

Thanks!

[William J. Bowman]

You might want `local-expand`. It can still give you something that is expanded
further than you want, unless you know exactly which identifier you want to stop
at, which you can specify in the stop list.
https://docs.racket-lang.org/reference/stxtrans.html#%28def._%28%28quote._~23~25kernel%29._local-expand%29%29

--
William J. Bowman

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[Thomas Del Vecchio]

Thanks so much! Using 

(with-syntax ([expanded-b (datum->syntax #'b (local-expand #'b 'expression #f))])

worked out great!

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