From f1ee00c759125e6532bf64ec6d78ee250e7265cc Mon Sep 17 00:00:00 2001
From: Luc Maisonobe <luc@apache.org>
Date: Sat, 21 Feb 2009 20:16:36 +0000
Subject: [PATCH] handle NaN and infinities correctly in the MathUtils.equals
 method with tolerance

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@746582 13f79535-47bb-0310-9956-ffa450edef68
---
 .../org/apache/commons/math/util/MathUtils.java    |  5 ++++-
 .../apache/commons/math/util/MathUtilsTest.java    | 14 +++++++++-----
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/java/org/apache/commons/math/util/MathUtils.java b/src/java/org/apache/commons/math/util/MathUtils.java
index 3e3a6fdef..a03f4b85d 100644
--- a/src/java/org/apache/commons/math/util/MathUtils.java
+++ b/src/java/org/apache/commons/math/util/MathUtils.java
@@ -373,6 +373,9 @@ public final class MathUtils {
     /**
      * Returns true iff both arguments are equal or within the range of allowed
      * error (inclusive).
+     * <p>
+     * Two NaNs are considered equals, as are two infinities with same size.
+     * </p>
      * 
      * @param x first value
      * @param y second value
@@ -380,7 +383,7 @@ public final class MathUtils {
      * @return true if the values are equal or within range of each other
      */
     public static boolean equals(double x, double y, double eps) {
-      return x == y || (x < y && (x + eps) >= y) || (x > y && x <= (y + eps));
+      return equals(x, y) || (Math.abs(y - x) <= eps);
     }
     
     /**
diff --git a/src/test/org/apache/commons/math/util/MathUtilsTest.java b/src/test/org/apache/commons/math/util/MathUtilsTest.java
index 20b61df09..6e75859a9 100644
--- a/src/test/org/apache/commons/math/util/MathUtilsTest.java
+++ b/src/test/org/apache/commons/math/util/MathUtilsTest.java
@@ -336,11 +336,15 @@ public final class MathUtilsTest extends TestCase {
     }
 
     public void testEqualsWithAllowedDelta() {
-        assertTrue(MathUtils.equals(153.0000, 153.0000, .0001));
-        assertTrue(MathUtils.equals(153.0000, 153.0001, .0001));
-        assertTrue(MathUtils.equals(152.9999, 153.0000, .0001));
-        assertFalse(MathUtils.equals(153.0000, 153.0001, .00001));
-        assertFalse(MathUtils.equals(152.9998, 153.0000, .0001));
+        assertTrue(MathUtils.equals(153.0000, 153.0000, .0625));
+        assertTrue(MathUtils.equals(153.0000, 153.0625, .0625));
+        assertTrue(MathUtils.equals(152.9375, 153.0000, .0625));
+        assertTrue(MathUtils.equals(Double.NaN, Double.NaN, 1.0));
+        assertTrue(MathUtils.equals(Double.POSITIVE_INFINITY, Double.POSITIVE_INFINITY, 1.0));
+        assertTrue(MathUtils.equals(Double.NEGATIVE_INFINITY, Double.NEGATIVE_INFINITY, 1.0));
+        assertFalse(MathUtils.equals(Double.NEGATIVE_INFINITY, Double.POSITIVE_INFINITY, 1.0));
+        assertFalse(MathUtils.equals(153.0000, 153.0625, .0624));
+        assertFalse(MathUtils.equals(152.9374, 153.0000, .0625));
     }
     
     public void testArrayEquals() {