Ah, okay, that makes sense, and fixed my issue. Thank you very much. ~Leif Andersen
On Thu, Dec 17, 2015 at 4:13 PM, Matthew Flatt <[email protected]> wrote: > A short answer: When compiling a submodule, as for any other module, > imported modules get fresh compile-time instantiations. It you want to > run effects from the enclosing module (which is an implicit import), > the effects must be in `begin-for-syntax`. > > > A long answer: > > When you write > > (module+ test ....) > > then all of the `test` parts are assembled together at the end of the > enclosing module in a single `(module* test #f ....)` form. > > So, > > (define-syntax x-top (stx-box #'yellow)) > > (splicing-let-syntax ([x (syntax-local-value #'x-top)]) > (module+ test > x)) > > (set-stx! x-top blue) > > (splicing-let-syntax ([x (syntax-local-value #'x-top)]) > (module+ test > x)) > > is the same as > > (define-syntax x-top (stx-box #'yellow)) > > (define-syntax x1 (syntax-local-value #'x-top)) > > (set-stx! x-top blue) > > (define-syntax x2 (syntax-local-value #'x-top)) > > (module* test #f > x1 > x2) > > where `x1` and `x2` each stand for `x` with some distinct scope. > > > By the time the enclosing module is expanded, but before its submodules > are expanded, that becomes > > (define-syntax x-top (stx-box #'yellow)) > > (define-syntax x1 (syntax-local-value #'x-top)) > > (void) > > (define-syntax x2 (syntax-local-value #'x-top)) > > (module* test #f > x1 > x2) > > Note that the `(set-stx! ....)` form has been macro-expanded away. > > The process of expanding the `test` module then creates a new > compile-time instantiation of the enclosing module. Since the > `set-stx!` form has been expanded away to `(void)`, there's no change > to `x-top` during that instantiation. > > > Replace the definition of `set-stx!` with > > (define-syntax (set-stx! stx) > (syntax-case stx () > [(_ box value) > #'(begin-for-syntax > (define-values (x y) (syntax-local-value/immediate #'box)) > (set-stx-box-stx! x #'value))])) > > Now, the expansion of the outer module is > > (define-syntax x-top (stx-box #'yellow)) > > (define-syntax x1 (syntax-local-value #'x-top)]) > > (begin-for-syntax > (define-values (x y) (syntax-local-value/immediate #'x-top)) > (set-stx-box-stx! x #'blue)) > > (define-syntax x2 (syntax-local-value #'x-top)]) > > (module* test #f > x1 > x2) > > As usual (i.e., as in sense of "Composable and Compilable Macros"), > using `begin-for-syntax` preserves the effect for all future > compile-time instantiations of the enclosing module. That way, you get > "yellow" followed by "blue", as you wanted. > > > > At Thu, 17 Dec 2015 15:08:06 -0500, Leif Andersen wrote: >> Hello, >> >> I am noticing that if I in the body of splicing-let-syntax I put a >> module+, or anything that lifts with >> syntax-local-lift-module-end-decloration really, The stuff that gets >> lifted out doesn't seem to match what I would expect it to. I suspect >> this is in part do to using prop:rename-transformer, and mutable >> structs, but I don't want to use a syntax-parameter because I would >> like to parameterize over an identifier. >> >> Here is the code I have: >> >> #lang racket >> >> (require racket/splicing) >> >> (define-syntax (yellow stx) #'"yellow") >> (define-syntax (blue stx) #'"blue") >> >> (begin-for-syntax >> (struct stx-box (stx) >> #:mutable >> #:transparent >> #:property prop:rename-transformer >> (lambda (inst) >> (syntax-property (stx-box-stx inst) 'not-free-identifier=? #t)))) >> (define-syntax (set-stx! stx) >> (syntax-case stx () >> [(_ box value) >> (begin >> (define-values (x y) (syntax-local-value/immediate #'box)) >> (set-stx-box-stx! x #'value) >> #'(void))])) >> >> (define-syntax x-top (stx-box #'yellow)) >> >> (define-syntax y-top 52) >> >> (splicing-let-syntax ([x (syntax-local-value #'x-top)]) >> (module+ test >> x)) >> >> (set-stx! x-top blue) >> >> (splicing-let-syntax ([x (syntax-local-value #'x-top)]) >> (module+ test >> x)) >> >> When I run it out I get: >> "yellow" >> "yellow" >> >> What I would like to get is: >> "yellow" >> "blue" >> >> Is there any better way to do this, and still have x be an identifier >> that is bound to the correct string? >> >> Thank you very much. >> >> ~Leif Andersen >> >> -- >> 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 [email protected]. >> 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
