Hello,
it seems to me that your example is unnecessary complicated.
Let's refactor it a bit before trying to obtain your goal.
First,
your example can be, for the purpose of your goal, simplified as :
(loop [a a0]
(if (predicate-fn a)
(return-fn a)
(recur (recur-fn a))))
So now, what can we do with this ?
you keep applying function recur-fn to a, starting with a = a0.
This is a job for iterate : (iterate recur-fn a0) will create this lazy
sequence starting with a0, and where each new value is made from (recur-fn
a)
Then you want to stop when predicate-fn returns true.
This is a job for remove, for example : (first (remove (comp not
predicate-fn) (iterate recur-fn a0)))
The final step is to apply return-fn to the result:
(return-fn
(first (remove
(comp not predicate-fn)
(iterate recur-fn a0)))
As for return-fn, predicate-fn and recur-fn :
(def b f1)
(def c (comp f2 b))
(def d (comp f3 c))
(def e (comp f4 d))
(def g (comp f5 c))
(def h (comp f5 f2))
(def return-fn e)
(def predicate-fn #(if (or (f6? (b %)) (<= (g %) (h %))))
(def recur-fn #(f7 (d a) (b a)))
Is it something like that you expected ?
2009/12/15 samppi <[email protected]>
> I'm trying to rewrite a loop to use higher-level functions instead.
> For pure functions f1, f2, f3, f4, f5, f6?, and f7, and a Clojure
> object a0, how can one rewrite the following loop to use map, reduce,
> etc.?
>
> (loop [a a0]
> (let [b (f1 a)
> c (f2 b)
> d (f3 c)
> e (f4 d)
> g (f5 c)
> h (-> e f2 f5)]
> (if (or (f6? b) (<= g h))
> e
> (recur (f7 d b)))))
>
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