Thanks for the counterexample. /Jens Axel
2014-04-03 15:46 GMT+02:00 Ryan Culpepper <ry...@ccs.neu.edu>: > On 04/03/2014 05:51 AM, Jens Axel Søgaard wrote: >> >> It seems the table needs to be created with #:phase -1. >> >> Since syntax-case uses a fender expression I added >> a begin in save-and-define, but it works either way >> (because free-id-table-set! returns a non-false value). >> >> #lang racket >> (require (for-syntax syntax/id-table)) >> >> (define-for-syntax table (make-free-id-table #:phase -1)) >> >> (define-syntax (save-and-define stx) >> (syntax-case stx () >> [(_ ID) >> (begin >> (free-id-table-set! table #'ID 1) >> #'(define ID 1))])) >> >> (define-syntax (load stx) >> (syntax-case stx () >> [(_ ID2) >> (if (free-id-table-ref table #'ID2 #f) >> #''ok >> #''different)])) >> >> (module+ test >> (save-and-define a) >> (displayln (load a))) > > > The code above is not correct. Here's a counterexample: > > (require (for-template (only-in racket/base [lambda x] [lambda y]))) > ;; x and y mean the same thing at phase -1 > (save-and-define x) > (load y) ;; => 'ok, but should be 'different > > The #:phase -1 means compare the for-template bindings, which is not what > you want. You want to compare the normal (phase-0) bindings, because the > identifiers are defined using plain old 'define'. See my other message for a > fix. > > As an aside, you should rarely-to-never use a constant phase number like -1. > Use (sub1 (syntax-local-phase-level)) instead. That way your code will still > work if required at a shifted phase (eg, for-syntax). > > Ryan > > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users -- -- Jens Axel Søgaard ____________________ Racket Users list: http://lists.racket-lang.org/users
