On Jul 12, 2011, at 9:32 AM, Bas Steunebrink wrote: > Wow, it was right under my nose! :-) Thanks! > > So I've been playing around with expand but it does not always return what > I'd expect, particularly with making fresh variables. For example: > > > (define-syntax m > (syntax-rules () > ((_ x) > (lambda (x) (lambda (y) x))))) > > (((m y) #t) #f) > #t ; OK > > (syntax->datum (expand '(m y))) > (#%expression (lambda (y) (lambda (y) y))) > > (((lambda (y) (lambda (y) y)) #t) #f) > #f ; So using the result of expand and syntax->datum gives something > different > > When expanding (m y), shouldn't at least one of the 2 y's be made fresh?
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." -- Matthias _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
