MATH-1130

Method "copyOfRange" (available as of Java 6 in "java.util.Arrays").


git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1604172 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -798,6 +798,21 @@ public class MathArrays {
          return output;
      }
 
+    /**
+     * Creates a copy of the {@code source} array.
+     *
+     * @param source Array to be copied.
+     * @param from Initial index of the range to be copied, inclusive.
+     * @param to Final index of the range to be copied, exclusive. (This index may lie outside the array.)
+     * @return the copied array.
+     */
+    public static double[] copyOfRange(double[] source, int from, int to) {
+        final int len = to - from;
+        final double[] output = new double[len];
+        System.arraycopy(source, from, output, 0, FastMath.min(len, source.length - from));
+        return output;
+     }
+
     /**
      * Compute a linear combination accurately.
      * This method computes the sum of the products

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

@@ -588,6 +588,29 @@ public class MathArraysTest {
         }
     }
 
+    @Test
+    public void testCopyOfRange() {
+        final double[] source = { Double.NEGATIVE_INFINITY,
+                                  -Double.MAX_VALUE,
+                                  -1, 0,
+                                  Double.MIN_VALUE,
+                                  FastMath.ulp(1d),
+                                  1, 3, 113, 4769,
+                                  Double.MAX_VALUE,
+                                  Double.POSITIVE_INFINITY };
+        final int from = 3;
+        final int to = source.length + 14;
+        final double[] dest = MathArrays.copyOfRange(source, from, to);
+
+        Assert.assertEquals(dest.length, to - from);
+        for (int i = from; i < source.length; i++) {
+            Assert.assertEquals(source[i], dest[i - from], 0);
+        }
+        for (int i = source.length; i < dest.length; i++) {
+            Assert.assertEquals(0, dest[i - from], 0);
+        }
+    }
+
     // MATH-1005
     @Test
     public void testLinearCombinationWithSingleElementArray() {