The documentation for `expand`: http://docs.racket-lang.org/reference/Expanding_Top-Level_Forms.html#%28def._%28%28quote._~23~25kernel%29._expand%29%29
says: "Expands all non-primitive syntax in top-level-form, and returns a syntax object for the expanded form that contains only core forms, matching the grammar specified by Fully Expanded Programs." The documentation for Fully Expanded Programs: http://docs.racket-lang.org/reference/syntax-model.html#%28part._fully-expanded%29 shows only #%plain-app -- _not_ #%app. But when I try the example for `expand`: (parameterize ([current-namespace (make-base-namespace)]) (syntax->datum (expand (datum->syntax #f '(module foo scheme (define a 3) (+ a 4)))))) I get: '(module foo scheme (#%module-begin (define-values (a) '3) (#%app call-with-values (lambda () (#%app + a '4)) print-values))) Notice that it uses #%app -- not #%plain-app. Apparently `expand` doesn't actually emit something that fits the spec for "Fully Expanded Programs". Guessing: Maybe the documentation -- and implementation -- of `expand` predates the addition to Racket of keyword arguments? Probably there is some extra expansion step, which creates the "lifted" #%plain-app wrappers for keyword argument functions I recall seeing in DrRacket's macro stepper? But ... how does one access this "extra" expansion step?? On Tue, Jan 21, 2014 at 9:09 PM, Patrick Boe <[email protected]> wrote: > Thanks, John. > > As you suggest, I'm trying to do exactly what the debugger is doing. As far > as I can tell by tracing through its code, the debugger does the following > to go from a raw datum ('(+ 1 2) in my example) to the syntax that it feeds > into annotate (this is boiled down from several hundred lines of unrelated > stuff in debug-tool.rkt) > > (expand-syntax > (expand-syntax-to-top-form > (namespace-syntax-introduce > (datum->syntax #f > '(+ 1 2))))) > > When I run this with racket from my command line, it fails with > > +: unbound identifier; > also, no #%app syntax transformer is bound > at: + > in: (+ 1 2) > context...: > /home/patrick/dev/scry/scree.rkt: [running body] > > I can wrap it with a call to (parameterize ([current-namespace > (make-base-namespace)]) ...), but then the resulting syntax is: > > #<syntax (#%app + (quote 1) (quote 2))> > > Which, as you can see, contains #%app instead of the #%plain-app that the > annotator is looking for. > > Huh. ____________________ Racket Users list: http://lists.racket-lang.org/users
