You wrote:
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As Matthias mentions, you can formally link together "units" together.
Units are Racket's dependency-injection component framework. You can
read documentation about them here:
http://docs.racket-lang.org/guide/units.html
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Thanks for the pointer, but unfortunately, the docs as they are don't seem
to provide a meaningful starting point for experimenting with the code, or
I may be too daft to make sense of it (probably the latter). Here's what I
did:
1. Copy-and-paste the four code fragments verbatim into four files named
(as the docs suggested) toy-factory-sig.rkt, simple-factory-unit.rkt,
toy-store-sig.rkt and toy-store-unit.rkt, respectively
2. Changed all require references to (require (file
"f://testpath//toy-store-sig.rkt")) etc because I couldn't find any other
way for wither DrRacket or Racket to accept the paths
3. (as the docs suggested) typed (require (file
"f://testpath//simple-factory-unit.rkt")) in DrRacket
DrRacket now responded with
..\..\install\racket\collects\syntax\modcode.rkt:46:8: load-handler:
expected a `module' declaration for `simple-factory-unit' in
#<path:f:\testpath\simple-factory-unit.rkt>, but found something else
looking through some older discussions, I discovered that the module
headers seem to be mandatory to be able to work with units, but they are
implicitly added when the language is set to racket/unit. I tried that on
the top level in DrRacket but would get the same error. I then tried
adding #lang racket/unit to all files but got this error:
f:\testpath\simple-factory-unit.rkt:1:0: #%module-begin: missing an
`import' clause in: (#%module-begin (require (file
"f://testpath//toy-factory-sig.rkt")) (define-unit simple-factory@
(import) (export toy-factory^) (printf "Factory started.\n")
(define-struct toy (color) #:transparent) (define (build-toys n) (for/list
((i (in-range n))) (make-toy (quote blue)))) (define (repaint t col)
(make-toy col))) (provide simple-factory@))
I would REALLY like to understand the concepts, but in order to do that, I
need to have working code that I can play around with. Could anybody
please provide a working instruction to get the code samples from the
documentation to run so I have a starting point? That means either provide
explicit module wrappers for the files or describe a way to set the
language such that the code runs as is?
Thanks again to this really great and dedicated community!
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