Added rint and round to DerivativeStructure.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1373780 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructure.java

@@ -386,6 +386,22 @@ public class DerivativeStructure implements FieldElement<DerivativeStructure>, S
                                        FastMath.floor(data[0]));
     }
 
+    /** Get the whole number that is the nearest to the instance, or the even one if x is exactly half way between two integers.
+     * @return a double number r such that r is an integer r - 0.5 <= this <= r + 0.5
+     */
+    public DerivativeStructure rint() {
+        return new DerivativeStructure(compiler.getFreeParameters(),
+                                       compiler.getOrder(),
+                                       FastMath.rint(data[0]));
+    }
+
+    /** Get the closest long to instance value.
+     * @return closest long to {@link #getValue()}
+     */
+    public long round() {
+        return FastMath.round(data[0]);
+    }
+
     /**
      * Returns the instance with the sign of the argument.
      * A NaN {@code sign} argument is treated as positive.

src/test/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructureTest.java

@@ -838,7 +838,7 @@ public class DerivativeStructureTest {
     }
 
     @Test
-    public void testCeilFloor() {
+    public void testCeilFloorRintLong() {
 
         DerivativeStructure x = new DerivativeStructure(1, 1, 0, -1.5);
         Assert.assertEquals(-1.5, x.getPartialDerivative(0), 1.0e-15);
@@ -847,6 +847,10 @@ public class DerivativeStructureTest {
         Assert.assertEquals(+0.0, x.ceil().getPartialDerivative(1), 1.0e-15);
         Assert.assertEquals(-2.0, x.floor().getPartialDerivative(0), 1.0e-15);
         Assert.assertEquals(+0.0, x.floor().getPartialDerivative(1), 1.0e-15);
+        Assert.assertEquals(-2.0, x.rint().getPartialDerivative(0), 1.0e-15);
+        Assert.assertEquals(+0.0, x.rint().getPartialDerivative(1), 1.0e-15);
+        Assert.assertEquals(-2.0, x.subtract(x.getField().getOne()).rint().getPartialDerivative(0), 1.0e-15);
+        Assert.assertEquals(-1l, x.round());
 
     }