CRRBV-29: Correct handling of reduce-kv for empty vectors

Author: jafingerhut

src/main/cljs/clojure/core/rrb_vector/rrbt.cljs

@@ -480,24 +480,26 @@
 
   IKVReduce
   (-kv-reduce [this f init]
-    (loop [i    0
-           j    0
-           init init
-           arr  (-array-for this i)
-           lim  (dec (alength arr))
-           step (inc lim)]
-      (let [init (f init (+ i j) (aget arr j))]
-        (if (reduced? init)
-          @init
-          (if (< j lim)
-            (recur i (inc j) init arr lim step)
-            (let [i (+ i step)]
-              (if (< i cnt)
-                (let [arr (-array-for this i)
-                      len (alength arr)
-                      lim (dec len)]
-                  (recur i 0 init arr lim len))
-                init)))))))
+    (if (zero? cnt)
+      init
+      (loop [i    0
+             j    0
+             init init
+             arr  (-array-for this i)
+             lim  (dec (alength arr))
+             step (inc lim)]
+        (let [init (f init (+ i j) (aget arr j))]
+          (if (reduced? init)
+            @init
+            (if (< j lim)
+              (recur i (inc j) init arr lim step)
+              (let [i (+ i step)]
+                (if (< i cnt)
+                  (let [arr (-array-for this i)
+                        len (alength arr)
+                        lim (dec len)]
+                    (recur i 0 init arr lim len))
+                  init))))))))
 
   IComparable
   (-compare [this that]

src/main/clojure/clojure/core/rrb_vector/rrbt.clj

@@ -1018,24 +1018,26 @@
 
   IKVReduce
   (kv-reduce [this f init]
-    (loop [i (int 0)
-           j (int 0)
-           init init
-           arr  (.arrayFor this i)
-           lim  (unchecked-dec-int (.alength am arr))
-           step (unchecked-inc-int lim)]
-      (let [init (f init (unchecked-add-int i j) (.aget am arr j))]
-        (if (reduced? init)
-          @init
-          (if (< j lim)
-            (recur i (unchecked-inc-int j) init arr lim step)
-            (let [i (unchecked-add-int i step)]
-              (if (< i cnt)
-                (let [arr (.arrayFor this i)
-                      len (.alength am arr)
-                      lim (unchecked-dec-int len)]
-                  (recur i (int 0) init arr lim len))
-                init)))))))
+    (if (zero? cnt)
+      init
+      (loop [i (int 0)
+             j (int 0)
+             init init
+             arr  (.arrayFor this i)
+             lim  (unchecked-dec-int (.alength am arr))
+             step (unchecked-inc-int lim)]
+        (let [init (f init (unchecked-add-int i j) (.aget am arr j))]
+          (if (reduced? init)
+            @init
+            (if (< j lim)
+              (recur i (unchecked-inc-int j) init arr lim step)
+              (let [i (unchecked-add-int i step)]
+                (if (< i cnt)
+                  (let [arr (.arrayFor this i)
+                        len (.alength am arr)
+                        lim (unchecked-dec-int len)]
+                    (recur i (int 0) init arr lim len))
+                  init))))))))
 
   CollFold
   ;; adapted from #'clojure.core.reducers/foldvec

src/test/cljs/clojure/core/rrb_vector/test_common.cljs

@@ -83,6 +83,14 @@
            (reduce + 0 (r/map identity (seq v1)))
            (reduce + 0 (r/map identity (seq v2)))))))
 
+(deftest test-reduce-3
+  (let [v0 (vec [])
+        rv0 (fv/vec [])]
+    (testing "reduce"
+      (is (= (reduce + v0) (reduce + rv0))))
+    (testing "reduce-kv"
+      (is (= (reduce-kv + 0 v0) (reduce-kv + 0 rv0))))))
+
 (deftest test-seq
   (let [v (fv/vec (range 128))
         s (seq v)]

src/test/clojure/clojure/core/rrb_vector/test_common.clj

@@ -83,6 +83,14 @@
            (reduce + 0 (r/map identity (seq v1)))
            (reduce + 0 (r/map identity (seq v2)))))))
 
+(deftest test-reduce-3
+  (let [v0 (vec [])
+        rv0 (fv/vec [])]
+    (testing "reduce"
+      (is (= (reduce + v0) (reduce + rv0))))
+    (testing "reduce-kv"
+      (is (= (reduce-kv + 0 v0) (reduce-kv + 0 rv0))))))
+
 (deftest test-seq
   (let [v (fv/vec (range 128))
         s (seq v)]