thanks Michel, the more realistic form was quite a bit longer, but i
will show just a piece of my (mis)direction
(defstruct Ruleform-struct
:rname :rule-seq
:if-cnt :then-cnt )
(defn rule-if-names [{:keys [ rule-seq if-cnt ] :as ruleform } ]
; (Camoflage Spotted Cover Action Use-Cover)
; ==> (Camoflage Spotted Cover)
(assoc ruleform :if-names
(take if-cnt rule-seq)) )
:
:
(defn rule-col-multiply [{:keys [ col-vectors ] :as ruleform } ]
; determine necessary increment for col counts to insure unique
lookup sums
; column unique items: [ 4 3 8 ] --index increments--> [1 4
12]
(assoc ruleform :col-multiply
(->> (reductions * (map count col-vectors))
(cons 1)
(drop-last))))
so basically I was trying to add about 7 additional attributes after
the initial creation. This was a part of a fuzzy state/rule engine
that was compiled for high speed, thought I would port from my
original Smalltalk version to Clojure. Well 'port' is the wrong word,
rewrite in a functional manner. I should use defrecord, but it gave
me fits first time I tried, so am keeping it simple for now.
thanks for the input & any further advice
On Nov 13, 10:48 am, Michel Alexandre Salim <michel
[email protected]> wrote:
> On Sat, 13 Nov 2010 06:31:03 -0800, garf wrote:
> > If I have a struct whose creation will require some function calls that
> > references some of its members, I am unsure how to go about it in a
> > clean way. For example:
> > (defstruct tz :a :b :c)
>
> > (def tz1 1 2 (+ (:a tz1) (:b tz1))
>
> Could you give a more realistic example of how you plan to use this?
>
> If the only restriction is that you only know the values for :a and :b at
> the time you want to create the structure, then this would work:
>
> (defn create-tz [a-val b-val]
> (struct-map tz :a a-val :b b-val :c (some-fn a-val b-val)))
>
> > will not work, but reflects the problem. Ideally at the end of this I
> > could do (:c tz1) and get 3 back. Any suggestions? Originally I had
> > used assocs, but that runs into the immutability problem, for example
>
> > (defstruct tz :a :b)
> > (def tz1 1 2)
> > (assoc tz1 :c (+ (:a tz1) (:b tz1))
>
> > does not actually update tz1
>
> Correct. Values are immutable, and in Clojure, even collections are
> values!
>
> If you want to have a variable hold a reference to some changing values
> then what you want is to use an atom or a ref. Atom is more easy to use,
> and unless you have several mutable values that need concurrent updating,
> is sufficient, so here's an example:
>
> > (def tz1 (atom (struct-map tz :a 1 :b 2)))
> #'user/tz1
> > @tz1
>
> {:a 1, :b 2, :c nil}> (swap! tz1 #(assoc % :c (+ (:a %) (:b %))))
> {:a 1, :b 2, :c 3}
> > @tz1
>
> {:a 1, :b 2, :c 3}
>
> Hope that helps,
>
> --
> Michel Alexandre Salim
> Clojure contributor:http://clojure.org/contributing
> GPG key ID: 78884778
>
> µblog:http://identi.ca/hircus | Jabber: [email protected]
> http://twitter.com/hircus| IRC: [email protected]
>
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