Add efficient rseq support

project.clj

@@ -3,7 +3,8 @@
   :license {:name "MIT License"
             :url "http://opensource.org/licenses/MIT"}
   :dependencies []
-  :profiles {:dev {:dependencies [[org.clojure/clojure "1.6.0"]
+  :profiles {:dev {:global-vars {*warn-on-reflection* true}
+                   :dependencies [[org.clojure/clojure "1.6.0"]
                                   [collection-check "0.1.2"]
                                   [criterium "0.4.3"]
                                   [primitive-math "0.1.3"]

src/immutable_int_map.clj

@@ -72,6 +72,13 @@
   (seq [this]
     (seq (.entries root (java.util.ArrayList.))))
 
+  clojure.lang.Reversible
+  (rseq [this]
+    (let [^java.util.ArrayList l
+          (.entries root (java.util.ArrayList.))
+          n (.size l)]
+      (for [i (range n)] (.get l (- n i 1)))))
+
   r/CollFold
 
   (coll-fold [this n combinef reducef]

test/immutable_int_map_test.clj

@@ -15,6 +15,23 @@
 (deftest test-map-like
   (check/assert-map-like 1e3 (i/int-map) gen/pos-int gen/int))
 
+(defn create-map-from-ints
+  [coll]
+  (reduce #(assoc %1 %2 %2) (i/int-map) coll))
+
+(def bunch-of-ints
+  (gen/fmap distinct (gen/list gen/pos-int)))
+
+(defspec sorted-sequence 1e3
+  (prop/for-all [xs bunch-of-ints]
+    (= (keys (seq (create-map-from-ints xs)))
+       (seq (sort xs)))))
+
+(defspec reverse-sorted-sequence 1e3
+  (prop/for-all [xs bunch-of-ints]
+    (= (keys (rseq (create-map-from-ints xs)))
+       (rseq (vec (sort xs))))))
+
 (def int-map-generator
   (gen/fmap
     (fn [ks]