If you want `splicing-parameterize` to compose with other macros that might implement definition forms, there's no fixed set of definition forms.
The other splicing forms use `local-expand` to detect definition forms, since the small set of core definition forms can be reliably detected in expanded code. See `splicing-let-body` within the implementation of `racket/splicing`. At Tue, 23 Jan 2018 17:15:10 -0800, Matthew Butterick wrote: > > > On Jan 22, 2018, at 7:22 PM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > > > > I think I've never considered `splicing-parameterize` because > > parameters can be mutated, but a `splicing-parameterize` form does make > > sense. I imagine that it would be implemented by creating a > > parameterization once, then pushing the parameterization over multiple > > expressions using `call-with-parameterization`. > > IIUC, to use `call-with-parameterization`, each expression needs to become > the > body of a thunk. This works for expressions that return a value. But forms > like `define` and `require` can't be used as the body of a thunk. So one has > to specially pluck them out. The example below works, albeit brutally. Is > there a more elegant pattern for picking out identifiers that cannot appear > as > the body of a thunk? > > > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > > #lang racket/base > (require racket/splicing > (for-syntax racket/base racket/syntax)) > > (define-syntax (splicing-parameterize stx) > (syntax-case stx () > [(_ ([PARAM VAL] ...) . BODY) > (with-syntax* ([PZATION (generate-temporary)] > [NEW-BODY (map (λ (stx) > (syntax-case stx () > [(ID ARG0 . ARGS) > (memq (syntax->datum #'ID) '(define > define-values)) ; ... and others > #'(ID ARG0 > (call-with-parameterization > PZATION (λ () (begin . ARGS))))] > [(ID . ARGS) > (memq (syntax->datum #'ID) '(require > provide splicing-let)) ; ... and others > #'(ID . ARGS)] > [OTHER #'(call-with-parameterization > PZATION (λ () OTHER))])) (syntax->list #'BODY))]) > #'(splicing-let ([PZATION (parameterize ([PARAM VAL] ...) > (current-parameterization))]) . NEW-BODY))])) > > (define my-param (make-parameter 0)) > > (splicing-parameterize ([my-param 42]) > (add1 (my-param)) > (sub1 (my-param))) ; prints 43 and 41 to repl > > (splicing-parameterize ([my-param 42]) > (define x (my-param)) > (check-equal? x 42) > (define-values (y z) (values (add1 (my-param)) (sub1 > (my-param))))) > > (splicing-parameterize ([my-param 42]) > (require rackunit)) > > (check-equal? x 42) > (check-equal? y 43) > (check-equal? z 41) -- 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.
