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
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