From aea8f3bcee9523df5f0a8d8a4cabc8084b667797 Mon Sep 17 00:00:00 2001
From: Alexander Udalov <Alexander.Udalov@jetbrains.com>
Date: Thu, 20 Jun 2013 21:04:42 +0400
Subject: [PATCH] Fix and test ProgressionUtil

Arithmetical modulo implementation was incorrect (-10 mod 1 == 0, but was 1)
---
 .../jetbrains/jet/ProgressionUtilTest.java    | 96 +++++++++++++++++++
 runtime/src/jet/runtime/ProgressionUtil.java  |  6 +-
 2 files changed, 100 insertions(+), 2 deletions(-)
 create mode 100644 compiler/tests/org/jetbrains/jet/ProgressionUtilTest.java

diff --git a/compiler/tests/org/jetbrains/jet/ProgressionUtilTest.java b/compiler/tests/org/jetbrains/jet/ProgressionUtilTest.java
new file mode 100644
index 00000000000..d03eff40fc5
--- /dev/null
+++ b/compiler/tests/org/jetbrains/jet/ProgressionUtilTest.java
@@ -0,0 +1,96 @@
+/*
+ * Copyright 2010-2013 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet;
+
+import jet.runtime.ProgressionUtil;
+import org.junit.Test;
+
+import static junit.framework.Assert.assertEquals;
+
+public class ProgressionUtilTest {
+    private static final int MAX = Integer.MAX_VALUE;
+    private static final int MIN = Integer.MIN_VALUE;
+
+    private static void doTest(int start, int end, int increment, int expected) {
+        int actualInt = ProgressionUtil.getProgressionFinalElement(start, end, increment);
+        assertEquals(expected, actualInt);
+
+        long actualLong = ProgressionUtil.getProgressionFinalElement((long) start, (long) end, (long) increment);
+        assertEquals(expected, actualLong);
+    }
+
+    private static final int[] INTERESTING = new int[]{ MIN, MIN / 2, -239, -23, -1, 0, 1, 42, 239, MAX / 2, MAX };
+
+    @Test
+    public void testGetFinalElement() {
+        // start == end
+        for (int x : INTERESTING) {
+            for (int increment : INTERESTING) if (increment != 0) {
+                doTest(x, x, increment, x);
+            }
+        }
+
+        // increment == 1
+        for (int start = 0; start < INTERESTING.length; start++) {
+            for (int end = start; end < INTERESTING.length; end++) {
+                doTest(INTERESTING[start], INTERESTING[end], 1, INTERESTING[end]);
+            }
+        }
+
+        // increment == -1
+        for (int end = 0; end < INTERESTING.length; end++) {
+            for (int start = end; start < INTERESTING.length; start++) {
+                doTest(INTERESTING[start], INTERESTING[end], -1, INTERESTING[end]);
+            }
+        }
+
+        // end == MAX
+        doTest(0, MAX, MAX, MAX);
+        doTest(0, MAX, MAX / 2, MAX - 1);
+        doTest(MIN + 1, MAX, MAX, MAX);
+        doTest(MAX - 7, MAX, 3, MAX - 1);
+        doTest(MAX - 7, MAX, MAX, MAX - 7);
+
+        // end == MIN
+        doTest(0, MIN, MIN, MIN);
+        doTest(0, MIN, MIN / 2, MIN);
+        doTest(MAX, MIN, MIN, -1);
+        doTest(MIN + 7, MIN, -3, MIN + 1);
+        doTest(MIN + 7, MIN, MIN, MIN + 7);
+
+        // Small tests
+        for (int start = -10; start < 10; start++) {
+            for (int end = -10; end < 10; end++) {
+                for (int increment = -20; increment < 20; increment++) {
+                    // Cut down incorrect test data
+                    if (increment == 0) continue;
+                    if ((increment > 0) != (start <= end)) continue;
+
+                    // Iterate over the progression and obtain the expected result
+                    int x = start;
+                    while (true) {
+                        int next = x + increment;
+                        if (next < Math.min(start, end) || next > Math.max(start, end)) break;
+                        x = next;
+                    }
+
+                    doTest(start, end, increment, x);
+                }
+            }
+        }
+    }
+}
diff --git a/runtime/src/jet/runtime/ProgressionUtil.java b/runtime/src/jet/runtime/ProgressionUtil.java
index a03226a82ce..876262c3e32 100644
--- a/runtime/src/jet/runtime/ProgressionUtil.java
+++ b/runtime/src/jet/runtime/ProgressionUtil.java
@@ -22,11 +22,13 @@ public class ProgressionUtil {
 
     // a mod b (in arithmetical sense)
     private static int mod(int a, int b) {
-        return a >= 0 ? a % b : a % b + b;
+        int mod = a % b;
+        return mod >= 0 ? mod : mod + b;
     }
 
     private static long mod(long a, long b) {
-        return a >= 0 ? a % b : a % b + b;
+        long mod = a % b;
+        return mod >= 0 ? mod : mod + b;
     }
 
     // (a - b) mod c