Added method multiply(int) to FieldElement, and updated implementing classes and tests accordingly. Solves MATH-684.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1178715 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/math/FieldElement.java

@@ -38,6 +38,16 @@ public interface FieldElement<T> {
      */
     T subtract(T a);
 
+    /** Compute n &times; this. Multiplication by an integer number is defined
+     * as the following sum
+     * <center>
+     * n &times; this = &sum;<sub>i=1</sub><sup>n</sup> this.
+     * </center>
+     * @param n Number of times {@code this} must be added to itself.
+     * @return A new element representing n &times; this.
+     */
+    T multiply(int n);
+
     /** Compute this &times; a.
      * @param a element to multiply
      * @return a new element representing this &times; a

src/main/java/org/apache/commons/math/complex/Complex.java

@@ -424,6 +424,25 @@ public class Complex implements FieldElement<Complex>, Serializable  {
                              real * factor.imaginary + imaginary * factor.real);
     }
 
+    /**
+     * Returns a {@code Complex} whose value is {@code this * factor}, with {@code factor}
+     * interpreted as a integer number.
+     *
+     * @param  factor value to be multiplied by this {@code Complex}.
+     * @return {@code this * factor}.
+     * @see #multiply(Complex)
+     */
+    public Complex multiply(final int factor) {
+        if (isNaN) {
+            return NaN;
+        }
+        if (Double.isInfinite(real) ||
+            Double.isInfinite(imaginary)) {
+            return INF;
+        }
+        return createComplex(real * factor, imaginary * factor);
+    }
+
     /**
      * Returns a {@code Complex} whose value is {@code this * factor}, with {@code factor}
      * interpreted as a real number.

src/main/java/org/apache/commons/math/util/BigReal.java

@@ -246,6 +246,11 @@ public class BigReal implements FieldElement<BigReal>, Comparable<BigReal>, Seri
         return new BigReal(d.multiply(a.d));
     }
 
+    /** {@inheritDoc} */
+    public BigReal multiply(final int n) {
+        return new BigReal(d.multiply(new BigDecimal(n)));
+    }
+
     /** {@inheritDoc} */
     public int compareTo(BigReal a) {
         return d.compareTo(a.d);
@@ -288,5 +293,4 @@ public class BigReal implements FieldElement<BigReal>, Comparable<BigReal>, Seri
     public Field<BigReal> getField() {
         return BigRealField.getInstance();
     }
-
 }

src/test/java/org/apache/commons/math/complex/ComplexTest.java

@@ -313,10 +313,12 @@ public class ComplexTest {
         Complex x = new Complex(3.0, 4.0);
         Complex z = x.multiply(Complex.NaN);
         Assert.assertSame(Complex.NaN, z);
+        z = Complex.NaN.multiply(5);
+        Assert.assertSame(Complex.NaN, z);
     }
 
     @Test
-    public void testMultiplyInInf() {
+    public void testMultiplyInfInf() {
         // Assert.assertTrue(infInf.multiply(infInf).isNaN()); // MATH-620
         Assert.assertTrue(infInf.multiply(infInf).isInfinite());
     }
@@ -351,6 +353,9 @@ public class ComplexTest {
         double yDouble = 2.0;
         Complex yComplex = new Complex(yDouble);
         Assert.assertEquals(x.multiply(yComplex), x.multiply(yDouble));
+        int zInt = -5;
+        Complex zComplex = new Complex(zInt);
+        Assert.assertEquals(x.multiply(zComplex), x.multiply(zInt));
     }
 
     @Test

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

@@ -87,6 +87,8 @@ public class BigRealTest {
         BigReal a = new BigReal("1024.0");
         BigReal b = new BigReal("0.0009765625");
         Assert.assertEquals(1.0, a.multiply(b).doubleValue(), 1.0e-15);
+        int n = 1024;
+        Assert.assertEquals(1.0, b.multiply(n).doubleValue(), 1.0e-15);
     }
 
     @Test