Replace :half-up rounding mode with :half-even

RoundingMode.HALF_EVEN is preferred over RoundingMode.HALF_UP to minimize rounding bias in repeated calculations.
sernamar · Sep 26, 2024 · ec9fad6 · ec9fad6
1 parent f336596
commit ec9fad6
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Showing 2 changed files with 10 additions and 10 deletions.
diff --git a/dev/arithmetic_operations_simulation.clj b/dev/arithmetic_operations_simulation.clj
@@ -17,12 +17,12 @@
 (defn rounded-money-simulation
   [money]
   (-> money
-      (core/add (core/rounded-money-of 1234567.3444 :eur 2 :half-up))
-      (core/subtract (core/rounded-money-of 232323 :eur 2 :half-up))
+      (core/add (core/rounded-money-of 1234567.3444 :eur 2 :half-even))
+      (core/subtract (core/rounded-money-of 232323 :eur 2 :half-even))
       (core/multiply 3.4)
       (core/divide 5.456)))
 
 (time
- (reduce (fn [acc _] (rounded-money-simulation acc)) (core/rounded-money-of 0 :eur 2 :half-up) (range 1000000)))
+ (reduce (fn [acc _] (rounded-money-simulation acc)) (core/rounded-money-of 0 :eur 2 :half-even) (range 1000000)))
 ;; => "Elapsed time: 7031.994195 msecs"
-;; => {:amount 1657407.95M, :currency :eur, :scale 2, :rounding-mode :half-up}
+;; => {:amount 1657407.95M, :currency :eur, :scale 2, :rounding-mode :half-even}
diff --git a/test/dinero/format_test.clj b/test/dinero/format_test.clj
@@ -30,7 +30,7 @@
         m2 (core/money-of 1 :btc)
         germany Locale/GERMANY]
     (t/is (= "1.234,57 €" (sut/format-money m1 {:locale germany
-                                                :rounding-mode :half-up
+                                                :rounding-mode :half-even
                                                 :decimal-places 2})))
     (t/is (= "1.234,56 €" (sut/format-money m1 {:locale germany
                                                 :rounding-mode :down
@@ -39,19 +39,19 @@
                                              :rounding-mode :down
                                              :decimal-places 0})))
     (t/is (= "1.234,57 €" (sut/format-money m1 {:locale germany
-                                                :rounding-mode :half-up
+                                                :rounding-mode :half-even
                                                 :decimal-places 2
                                                 :symbol-style :symbol})))
     (t/is (= "1.234,57 EUR" (sut/format-money m1 {:locale germany
-                                                  :rounding-mode :half-up
+                                                  :rounding-mode :half-even
                                                   :decimal-places 2
                                                   :symbol-style :code})))
     (t/is (= "1,00 ₿" (sut/format-money m2 {:locale germany
-                                            :rounding-mode :half-up
+                                            :rounding-mode :half-even
                                             :decimal-places 2
                                             :symbol-style :symbol})))
     (t/is (= "1,00 BTC" (sut/format-money m2 {:locale germany
-                                              :rounding-mode :half-up
+                                              :rounding-mode :half-even
                                               :decimal-places 2
                                               :symbol-style :code})))))
 
@@ -65,5 +65,5 @@
     (t/is (= "1.234,568 €" (sut/format-money-with-pattern money "#,##0.000 ¤" {:locale germany})))
     (t/is (= "1,234.57 £" (sut/format-money-with-pattern money "#,##0.00 ¤" {:locale uk})))
     (t/is (= "1,234.57 GBP" (sut/format-money-with-pattern money "#,##0.00 ¤¤" {:locale uk})))
-    (t/is (= "1.234,57 €" (sut/format-money-with-pattern money "#,##0.00 ¤" {:locale germany :rounding-mode :half-up})))
+    (t/is (= "1.234,57 €" (sut/format-money-with-pattern money "#,##0.00 ¤" {:locale germany :rounding-mode :half-even})))
     (t/is (= "1.234,56 €" (sut/format-money-with-pattern money "#,##0.00 ¤" {:locale germany :rounding-mode :down})))))