Implement iterate

Author: daveray

language-adaptors/rxjava-clojure/src/main/clojure/rx/lang/clojure/core.clj

@@ -4,7 +4,7 @@
                             empty every?
                             filter first future
                             group-by
-                            interleave interpose into
+                            interleave interpose into iterate
                             keep keep-indexed
                             map mapcat map-indexed
                             merge next nth partition-all reduce reductions
@@ -550,6 +550,19 @@
   ; same thread, so we can't do that here.
   (reduce conj to from))
 
+(defn iterate
+  "Returns an Observable of x, (f x), (f (f x)) etc. f must be free of side-effects
+
+  See:
+    clojure.core/iterate
+  "
+  [f x]
+  (observable* (fn [s]
+                 (loop [x x]
+                   (when-not (unsubscribed? s)
+                     (on-next s x)
+                     (recur (f x)))))))
+
 (defn keep
   [f xs]
   (filter (complement nil?) (map f xs)))

language-adaptors/rxjava-clojure/src/test/clojure/rx/lang/clojure/core_test.clj

@@ -348,6 +348,14 @@
        {} []
        '() (range 50)))
 
+(deftest test-iterate
+  (are [f x n] (= (->> (iterate f x) (take n))
+                  (->> (rx/iterate f x) (rx/take n) (b/into [])))
+       inc 0 10
+       dec 20 100
+       #(conj % (count %)) [] 5
+       #(cons (count %) % ) nil 5))
+
 (deftest test-keep
   (is (= (into [] (keep identity [true true false]))
          (b/into [] (rx/keep identity (rx/seq->o [true true false])))))