omg thank you so much!! that's just what I want it! 2010/11/13 Thomas Chust <ch...@web.de>
> 2010/11/13 김태윤 <kty1...@gmail.com>: > > [...] > > I was told by mailing list that read the racket guide unit section > > but sorry I still don't understand. > > [...] > > Hello, > > you have to use units here because modules do not allow mutually recursive > dependencies. An example for your situation may look like this: > > -----BEGIN "ab-sig.rkt"----- > #lang racket > > (define-signature a^ > (a)) > > (define-signature b^ > (b)) > > (provide > (all-defined-out)) > -----END "ab-sig.rkt"----- > > -----BEGIN "a.rkt"----- > #lang racket > (require > "ab-sig.rkt") > > (define-unit a@ > (import b^) > (export a^) > (define a 1) > (printf "a@ sees b = ~s~%" b)) > > (provide > (all-defined-out)) > -----END "a.rkt"----- > > -----BEGIN "b.rkt"----- > #lang racket > (require > "ab-sig.rkt") > > (define-unit b@ > (import a^) > (export b^) > (define b 2) > (printf "b@ sees a = ~s~%" a)) > > (provide > (all-defined-out)) > -----END "b.rkt"----- > > -----BEGIN "ab.rkt"----- > #lang racket > (require > "ab-sig.rkt" "a.rkt" "b.rkt") > > (define-values/invoke-unit/infer > (export a^ b^) > (link a@ b@)) > > (printf "ab.rkt sees a = ~s~%" a) > (printf "ab.rkt sees b = ~s~%" b) > -----END "ab.rkt"----- > > As you can see, the module dependencies are cycle free but the unit > dependency > between a@ and b@ is mutual. > > Note that, even though a@ and b@ can see each other's variables exported > through > the signatures a^ and b^ respectively, the units still have to be > initialized > in some order and hence one of the printf calls in a@ or b@ will show an > undefined value when "ab.rkt" is run. > > I hope this helps :-) > > Ciao, > Thomas > > > -- > When C++ is your hammer, every problem looks like your thumb. >
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