I think you want to use `expand' and `eval-syntax', and avoid `syntax->datum' entirely.
On Tue, Jul 12, 2011 at 10:30 AM, Bas Steunebrink <b...@idsia.ch> wrote: > Thanks Matthias and Eli, I understand what expand does and that > syntax->datum throws away too much (by design). Still my question remains of > how to obtain a datum that is equivalent to a given quoted expression (when > eval'ed) but with all macros expanded (generating fresh symbols where > necessary). So does there exist a function syntax->datum* such that: > >> (define-syntax m > (syntax-rules () > ((_ x) > (lambda (x) (lambda (y) x))))) >> (((m y) #t) #f) > #t ; OK >> (syntax->datum* (expand '(m y))) > (lambda (y) (lambda (g42) y)) ; g42 is a fresh symbol >> (((eval (syntax->datum* (expand '(m y)))) #t) #f) > #t ; using Racket's syntax->datum gives #f > > Please note that I'm really interested in getting just the macro-expanded > datum (otherwise I would've been done already!). > > > Thanks again for your kind help, > Bas > > > > > On 7/12/11 16:17 PM, Matthias Felleisen wrote: >> >> >> On Jul 12, 2011, at 10:16 AM, Eli Barzilay wrote: >> >>> 8 minutes ago, Matthias Felleisen wrote: >>>> >>>> The following experiment produces a bit more insight: >>>> >>>>> (((eval (expand '(m y))) #t) #f) >>>> >>>> #t >>>> >>>> The result of expand compiles to the correct closure. >>>> >>>> So the docs for syntax->datum are dead serious when they say that it >>>> "returns a datum by stripping the lexical information, source >>>> location information, properties, and tamper status from stx." >>> >>> Try also the macro stepper. From an upcoming package for the repl: >>> >>> -> (define-syntax m >>> (syntax-rules () >>> ((_ x) >>> (lambda (x) (lambda (y) x))))) >>> -> ,stx (m y) * >>> syntax set >>> stepper: >>> Macro transformation >>> (m y) >>> ==> >>> (lambda:1 (y) (lambda:1 (y:1) y)) >>> >>> (But you'd usually want to use the gui version...) >> >> Fire up drracket and run the stepper. > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users > -- sam th sa...@ccs.neu.edu _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
