MATH-843

Corrected documentation for "Precision.EPSILON".


git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1370547 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/math3/util/Precision.java

@@ -30,8 +30,8 @@ import org.apache.commons.math3.exception.util.LocalizedFormats;
  */
 public class Precision {
     /**
-     * Smallest positive number such that {@code 1 - EPSILON} is not
-     * numerically equal to 1.
+     * Largest double-precision floating-point number such that
+     * {@code 1 + EPSILON} is numerically equal to 1.
      * <br/>
      * In IEEE 754 arithmetic, this is 2<sup>-53</sup>.
      */

src/test/java/org/apache/commons/math3/util/PrecisionTest.java

@@ -488,4 +488,16 @@ public class PrecisionTest {
 
         Assert.assertTrue(nonRepresentableCount / (double) numTrials > 0.9);
     }
+
+    @Test
+    public void testMath843() {
+        final double afterEpsilon = FastMath.nextAfter(Precision.EPSILON,
+                                                       Double.POSITIVE_INFINITY);
+
+        // a) 1 + EPSILON is equal to 1.
+        Assert.assertTrue(1 + Precision.EPSILON == 1);
+
+        // b) 1 + "the number after EPSILON" is not equal to 1.
+        Assert.assertFalse(1 + afterEpsilon == 1);
+    }
 }