Hi,
After (are-friends bill bob) they should be friends,
so I tried @bob
and don't see bill as a friend. why?
@bob
{:friends #{#<Ref clojure.lang....@165ab39>}, :name "Bob"}
-sun
On Jan 10, 9:44 pm, Stuart Sierra <the.stuart.sie...@gmail.com> wrote:
> Hi Patrick,
>
> Here's one way to do it:
>
> (defn new-person [name]
> (ref {:name name, :friends #{}}))
>
> (defn are-friends [a b]
> (dosync
> (commute a assoc :friends (conj (:friends @a) b))
> (commute b assoc :friends (conj (:friends @b) a))))
>
> (def bill (new-person "Bill"))
> (def bob (new-person "Bob"))
>
> (are-friends bill bob)
>
> -Stuart Sierrra
>
> On Jan 10, 8:39 pm, CuppoJava <patrickli_2...@hotmail.com> wrote:
>
> > Hello,
> > I'm stumped as to how I create a mutually referential data structure
> > in Clojure. My compsci is fuzzy. I don't know if what I'm trying to do
> > is possible. Any insight would be helpful.
>
> > I have a function that creates a Person, given his name and a list of
> > friends.
>
> > (defn new_person [name & friends]
> > {:name name
> > :friends friends})
>
> > But how do I create a mutually referential definition?
>
> > ie. what if Bob is Bill's friend, and Bill is also Bob's friend?
> > I would have to do something like the following: (which is not
> > allowed)
>
> > (def bob (new_person "Bob" bill)) <-Not allowed: forward reference.
> > (def bill (new_person "Bill" bob))
>
> > Thanks a lot for your help
> > -Patrick
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