added compareTo method with epsilon

JIRA: MATH-247

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@749139 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/math/util/MathUtils.java

@@ -347,6 +347,25 @@ public final class MathUtils {
         return logSum;      
     }
     
+    /**
+     * Compares two numbers given some amount of allowed error.
+     * 
+     * @param x the first number
+     * @param y the second number
+     * @param eps the amount of error to allow when checking for equality
+     * @return <ul><li>0 if  {@link #equals(double, double, double) equals(x, y, eps)}</li>
+     *       <li>&lt; 0 if !{@link #equals(double, double, double) equals(x, y, eps)} &amp;&amp; x &lt; y</li>
+     *       <li>> 0 if !{@link #equals(double, double, double) equals(x, y, eps)} &amp;&amp; x > y</li></ul>
+     */
+    public static int compareTo(double x, double y, double eps) {
+        if (equals(x, y, eps)) {
+            return 0;
+        } else if (x < y) {
+          return -1;
+        }
+        return 1;
+    }
+    
     /**
      * Returns the <a href="http://mathworld.wolfram.com/HyperbolicCosine.html">
      * hyperbolic cosine</a> of x.

src/test/org/apache/commons/math/util/MathUtilsTest.java

@@ -305,6 +305,12 @@ public final class MathUtilsTest extends TestCase {
             .isInfinite(x));
     }
 
+    public void testCompareTo() {
+      assertEquals(0, MathUtils.compareTo(152.33, 152.32, .011));
+      assertTrue(MathUtils.compareTo(152.308, 152.32, .011) < 0);
+      assertTrue(MathUtils.compareTo(152.33, 152.318, .011) > 0);
+    }
+    
     public void testCosh() {
         double x = 3.0;
         double expected = 10.06766;