Off-topic, but FWIW, you need set! in the list of literals for syntax-case.
Otherwise, you could have a spurious match.
(define-syntax test
(make-set!-transformer
(λ (stx)
(syntax-case stx ()
[(set! id v)
#'(println '(set! id v))]))))
(test 1 2) ;=> '(test 1 2)
(set! test 3) ;=> '(set! test 3)
(define-syntax test2
(make-set!-transformer
(λ (stx)
(syntax-case stx (set!)
[(set! id v)
#'(println '(set! id v))]))))
#;(test2 1 2) ;=> bad syntax
(set! test2 3) ;=> '(set! test2 3)
On Thu, Mar 10, 2022 at 11:57 PM 'William J. Bowman' via Racket Developers <
[email protected]> wrote:
> shhyou helped me figure this out; it was really my fault, as I was
> generating a new set!-transformer each time through the loop, instead of a
> call to a single transformer.
>
>
> https://gist.github.com/shhyou/ff5366e8469d4da8f54d262a52744f30#file-bind-it-rkt
>
> Fell in a standard macro trap.
>
> --
> William J. Bowman
>
> On Thu, Mar 10, 2022 at 08:49:46PM -0800, 'William J. Bowman' via Racket
> Developers wrote:
> > I've extracted a piece of a language implementation here (also attached)
> > https://gist.github.com/wilbowma/87d7e18718e08968cc4b2d003efbff2b
> >
> > It provides two implementations of a little language that provides an
> unbounded
> > number of implicit global mutable variables.
> > I decided to bind the first 1000 of them because I figure no user would
> generate
> > that many, instead of doing anything clever.
> >
> > One method uses `let-syntax` and implements these variables with set!
> > transformers, and the other just binds the variables with `let`.
> >
> > It seems the version that uses `let-syntax` runs in time directly
> proportional
> > to the number of these variables I decide to bind, i.e., the number of
> macros I
> > introduce via `let-syntax`; about 1ms per variable bound, regardless of
> whether
> > the macros are ever used.
> >
> > This behaviour surprised me a lot. Is this expected?
> >
> > --
> > William J. Bowman
> >
> > --
> > You received this message because you are subscribed to the Google
> Groups "Racket Developers" group.
> > To unsubscribe from this group and stop receiving emails from it, send
> an email to [email protected].
> > To view this discussion on the web visit
> https://groups.google.com/d/msgid/racket-dev/YirU6gt5MxSnLcvf%40williamjbowman.com
> .
>
> > #lang racket
> > (require (for-syntax racket/syntax))
> >
> > #|
> > 1,000 fvars; let-syntax implementation
> > cpu time: 1162 real time: 1165 gc time: 156
> >
> > 10,000 fvars; let-syntax implementation
> > cpu time: 10928 real time: 10964 gc time: 1374
> >
> > 1,000 fvars; let implementation
> > cpu time: 20 real time: 20 gc time: 3
> >
> > 10,000 fvars; let implementation
> > cpu time: 225 real time: 225 gc time: 54
> > |#
> >
> > (begin-for-syntax
> > (define current-fvars (make-parameter 10000))
> >
> > (define (bind-fvars s n tail)
> > #`(let-syntax
> > #,(for/list ([i (in-range 0 n)])
> > (with-syntax ([fvar (syntax-local-introduce (format-id #f
> "fv~a" i))]
> > [offset i]
> > [stack s])
> > #`[fvar (make-set!-transformer
> > (lambda (stx)
> > (syntax-case stx ()
> > [(set! id v)
> > #`(vector-set! stack offset v)]
> > [id (identifier? #'id)
> > #`(vector-ref stack offset)])))]))
> > #,tail)))
> >
> > (define-syntax (my-module stx)
> > (syntax-case stx ()
> > [(_ e ...)
> > (with-syntax ([s #'stack])
> > #`(let ([s (make-vector #,(current-fvars) (void))])
> > #,(bind-fvars #'s (current-fvars) #`(begin e ...))))]))
> >
> > (define-namespace-anchor a)
> >
> > (displayln "1,000 fvars; let-syntax implementation")
> >
> > (time
> > (eval
> > '(begin
> > (begin-for-syntax
> > (current-fvars 1000))
> > (my-module
> > (set! fv0 8)
> > (set! fv1 8)
> > (+ fv0 fv1)))
> > (namespace-anchor->namespace a)))
> >
> > (displayln "10,000 fvars; let-syntax implementation")
> >
> > (time
> > (eval
> > '(begin
> > (begin-for-syntax
> > (current-fvars 10000))
> > (my-module
> > (set! fv0 8)
> > (set! fv1 8)
> > (+ fv0 fv1)))
> > (namespace-anchor->namespace a)))
> >
> > (define-for-syntax (bind-fvars2 n tail)
> > #`(let #,(for/list ([i (in-range 0 n)])
> > (with-syntax ([fvar (syntax-local-introduce (format-id #f
> "fv~a" i))])
> > #`[fvar (void)]))
> > #,tail))
> >
> > (define-syntax (my-module2 stx)
> > (syntax-case stx ()
> > [(_ e ...)
> > (bind-fvars2 (current-fvars) #`(begin e ...))]))
> >
> > ;; expansion time increases with the number of let bindings, but not
> nearly as bad
> > ;; expansion time seems to be 1ms per fvar, i.e., per let-syntax?
> >
> > (displayln "1,000 fvars; let implementation")
> >
> > (time
> > (eval
> > '(begin
> > (begin-for-syntax
> > (current-fvars 1000))
> > (my-module2
> > (set! fv0 8)
> > (set! fv1 8)
> > (+ fv0 fv1)))
> > (namespace-anchor->namespace a)))
> >
> > (displayln "10,000 fvars; let implementation")
> > (time
> > (eval
> > '(begin
> > (begin-for-syntax
> > (current-fvars 10000))
> > (my-module2
> > (set! fv0 8)
> > (set! fv1 8)
> > (+ fv0 fv1)))
> > (namespace-anchor->namespace a)))
>
> --
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> To view this discussion on the web visit
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> .
>
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