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Add the iterator transducing context

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Christophe Grand 2017-10-18 14:39:50 -05:00
parent b96d9d7994
commit 51b61f3889
1 changed files with 25 additions and 0 deletions
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src/net/cgrand/xforms.cljc
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@ -468,6 +468,31 @@
(vreset! vi (let [i (inc i)] (if (= n i) 0 i)))
(rf acc (f (vreset! vwacc (f (invf wacc x') x))))))))))))
#?(:clj
(defn iterator
"Iterator transducing context, returns an iterator on the transformed data.
Equivalent to (.iterator (eduction xform (iterator-seq src-iterator))) except there's is no buffering on values (as in iterator-seq),
This buffering may cause problems when mutable objects are returned by the src-iterator."
[xform ^java.util.Iterator src-iterator]
(let [NULL (Object.)
dq (java.util.ArrayDeque. 32)
rf (xform (fn ([acc] acc) ([acc x] (.push dq (if (some? x) x NULL)) acc)))
vopen (volatile! true)
ensure-next #(or (some? (.peek dq))
(if (and @vopen (.hasNext src-iterator))
(let [acc (rf nil (.next src-iterator))]
(when (reduced? acc) (vreset! vopen false))
(recur))
false))]
(reify java.util.Iterator
(hasNext [_]
(ensure-next))
(next [_]
(if (ensure-next)
(let [x (.poll dq)]
(if (identical? NULL x) nil x))
(throw (java.util.NoSuchElementException.))))))))
#?(:clj
(defn window-by-time
"ALPHA