Hello, I posted a question on stackoverflow this week: http://stackoverflow.com/questions/6838115/racket-using-a-macro-across-modules, with thanks to Eli, I was able to understand where I was going wrong. I took his advice in using a struct-info alternative, and as I have limited experience building macros I'm appealing for comments on my solution.
The macro in question destructively increments a field in a structure. In this version, the getter and setter are pulled from extract-struct-info. I was hoping that I could locate the getter (and setter) with just the field and structure type but that information doesn't seem to be possible. https://gist.github.com/1111993 Thanks, - Tom (for completeness, contents of the gist above) #lang racket (require (for-syntax racket/struct-info)) (require rackunit) ;; (increment! a-struct type field [amount 1]) -> void ;; increments a mutable field in a structure (define-syntax (increment! stx) (syntax-case stx () [(_ s sn fn i) (with-syntax ([(_ _ _ getters setters _) (extract-struct-info (syntax-local-value #'sn))]) (let ([seek (string->symbol (format "~a-~a" (syntax-e #'sn) (syntax-e #'fn)))]) (let iter ([gets (syntax->list #'getters)] [sets (syntax->list #'setters)]) (cond [(null? gets) (raise-syntax-error #f "unknown field-name" stx)] [(eq? (syntax-e (car gets)) seek) (if (identifier? (car sets)) (with-syntax ([set! (car sets)] [get (car gets)]) #'(set! s (+ i (get s)))) (raise-syntax-error #f (format "~s not mutable" (syntax-e #'fn)) stx))] [else (iter (cdr gets) (cdr sets))]))))] [(increment! s sn fn) #'(increment! s sn fn 1)])) (struct vault ([dollars #:mutable] pounds [euros #:mutable])) (define v (vault 0 50 20)) (increment! v vault dollars 100) (increment! v vault euros) (test-case "sums" (check-equal? (vault-dollars v) 100) (check-equal? (vault-euros v) 21)) ;(test-exn "not mutable" exn:fail:syntax? (λ () (increment! v vault pounds))) ;(test-exn "unknown name" exn:fail:syntax? (λ () (increment! v vault yen))) _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
