On Mon, Nov 15, 2010 at 2:35 PM, trying clj <trying...@gmail.com> wrote:
> File example\some.clj
>
> (ns example.some (:use example.someother))
>
> (defn helloworld [] (print "helloworld"))
>
>
> File example\someother.clj:
>
> (ns example.someother (:use example.some))
>
> (defn sample [] (helloworld))
>
>
> A compile error "Unable to resolve helloworld in this context" is produced
> (on either latest clojure-maven-plugin or Leiningen). If the two defn's are
> switched places, the build completes successfully.
>
> This is very basic functionality but after thinking a lot, I still see no
> reason why it isn't working. What am I getting wrong?
Probably in one case it was compiling the file with sample before the
file with helloworld. Be glad this example doesn't have a true
circular dependency.
I have sometimes resorted to atom to get rid of circular dependencies:
file1.clj:
(defvar- foo (atom nil))
(defn some-fn [...]
...
(do-something-with @foo)
...)
(defn set-foo! [x]
(reset! foo x))
file2.clj:
(defn some-other-fn [...]
...
(some-fn some-args)
...)
(defn init-file2 []
(set-foo! [some-data-structure-built-using-some-other-fn]))
filen.clj:
(defn main- [...]
(init-file2)
...)
Obviously in this example some-fn ought to have some way to be
somewhat useful if the atom's still its initial value, here nil. A
case that comes up sometimes is a lookup table, in which case starting
it with an empty map {} makes sense. The most recent case where I did
something like this, foo was a large data structure that had to hold
functions that called functions that called functions that,
eventually, referenced the data structure. None of these functions
would actually get *called* until bootstrap was complete, so they'd
never see the atom holding nil, but fn1 calls fn2 calls fn3 calls fn4
references foo contains fn1 is still a circular dependency.
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