I should've been clear that the loop example was taken from the Chicken scheme wiki. Same for the while example mentioned in the email: https://wiki.call-cc.org/man/4/Macros#ir-macro-transformer
Using the syntax->datum here would drop lexical information though; if the syntax object given to the macro has lexical context other than the use-site of the macro, binding information will be lost. (define-syntax (use-loop stx) (syntax-case stx () [(_ body) #'(loop (displayln "loop") body (exit))])) (let ([i 0]) (loop (displayln "loop") (displayln i) (exit))) (let ([i 0]) (use-loop (displayln i))) On Wed, Aug 29, 2018 at 4:32 PM, t791bc via Racket Users <email@example.com> wrote: > Thanks for the responses. In case anybody is interested, I came up with the > following implementation. Since (at least in this simple implementation) > there is an obvious symmetry between explicit renaming and implicit renaming > I added the er-macro-transformer also. They seem to work correctly. One > minor difference to the ir-macro-transformer in Chicken though is that > parameters also need to be injected (which kind of logically makes sense). > > I am not exactly sure whether datum->syntax and syntax->datum go through the > entire expression but if they do, the implementation will be very > inefficient. (If anybody knows more on that, I would be interested.) > > Implementation: > > #lang racket > > (provide (for-syntax ir-macro-transformer er-macro-transformer)) > > (begin-for-syntax > (require (for-syntax (only-in racket/base lambda syntax with-syntax))) > (define-syntax ir-macro-transformer > (lambda (stx) > (with-syntax ([(_ proc) stx]) > #'(lambda (x) > (datum->syntax #'proc (proc (syntax->datum x) (lambda (v) > (datum->syntax x v)))))))) > (define-syntax er-macro-transformer > (lambda (stx) > (with-syntax ([(_ proc) stx]) > #'(lambda (x) > (datum->syntax x (proc (syntax->datum x) (lambda (v) > (datum->syntax #'proc v))))))))) > > Examples: > > ; loop example from Shu-Hung's post is now working as expected > > (define-syntax loop > (ir-macro-transformer > (lambda (expr inject) > (let ((body (cdr expr))) > `(call-with-current-continuation > (lambda (,(inject 'exit)) > (let f () (begin .,(inject body)) (f)))))))) ; notice the > (inject body) here... dropping the inject will break the code > > ;=> 543210 > > ; the following suggests that the lexical environments work as they should > > (let ([x 1] > [y 2]) > (swap! x y) > x) > > => 2 > > (define t 3) > > (define-syntax tripple > (ir-macro-transformer > (lambda (expr inject) > (let ([a (cadr expr)]) > `(* t ,(inject a)))))) > > (let ([t 29] > [* -]) > (tripple 2)) > > ;=> 6 > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.