This probably isn't the right way to do it, but it works:
user=> (def n0 {:in (atom ()) :out (atom '(#'n1))})
#'user/n0
user=> (def n1 {:in (atom '(#'n0)) :out (atom ())})
#'user/n1
user=> (swap! (:in n0) conj '#'n3)
((var n3))
user=> n0
{:in #<a...@47ef7de4: ((var n3))>, :out #<a...@3c3228a1: ((var n1))>}
user=> @(eval (first @(:in n1)))
{:in #<a...@47ef7de4: ((var n3))>, :out #<a...@3c3228a1: ((var n1))>}
I'm not sure whether it's faster to use eval in this case, or the whole STM
thing.
Thoughts?
Disclaimer: I'm a n00b too! :-p
On Jul 2, 2010, at 5:21 PM, Laurent PETIT wrote:
> I've also struggled with the same concepts in my head in the past.
>
> One answer to try explain why it is not possible, is that if you do
> that, you somehow try to conflate identity and state again.
>
> When you write n0: in () out (n1) and n1 in(n0) out() , it seems to me
> that when you write n0:in() out(n1) you're thinking about n0 as the
> node(identity)+state (value of an identity at a point in time)
> conflated, but when you write n1 in(n0) out(), you think about n0 as
> the identity.
>
> So in fact, if I try to separate identity and state again, n0 and n1 are refs:
> (def n0 (ref nil))
> (def n1 (ref {:in [n0], :out []}))
> (dosync (ref-set n0 {:in [], :out [n1]}))
>
> Or you could manage by yourself the concept of identity, not
> delegating it to clojure's refs, as you said.
>
>
> 2010/7/2 Mate Toth <[email protected]>:
>> I'm building a directed graph library, where the nodes has "out" and
>> "in" fields. If I connect a node, let's say:
>> (node->node n0 n1)
>> then the node's fields would be the following:
>>
>> n0:
>> in: ()
>> out: (n1)
>>
>> n1:
>> in: (n0)
>> out ()
>>
>>
>> My problem is that if I update n0 I could only add the old "instance"
>> to the list, so when I update n1, n0's out field would would contain
>> an outdated n1 also..
>>
>> So n00b head I think it's out of the functional paradigm(or I could
>> use node-ids and a hash as a graph, but I don't like it), but how you
>> guys would solve this problem? Any workaround?
>>
>> Thanks for your help! M
>>
>>
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