Added unit tests for matrix with scalar multiplication.

src/Numerics/LinearAlgebra/Double/Matrix.Arithmetic.cs

@@ -38,57 +38,6 @@ namespace MathNet.Numerics.LinearAlgebra.Double
     /// </summary>
     public abstract partial class Matrix
     {
-        /// <summary>
-        /// Multiplies each element of this matrix with a scalar.
-        /// </summary>
-        /// <param name="scalar">The scalar to multiply with.</param>
-        public virtual void Multiply(double scalar)
-        {
-            if (Precision.AlmostEqualInDecimalPlaces(1.0, scalar, 15))
-            {
-                return;
-            }
-
-            Parallel.For(
-                0,
-                RowCount,
-                i =>
-                {
-                    for (int j = 0; j < ColumnCount; j++)
-                    {
-                        At(i, j, At(i, j) * scalar);
-                    }
-                });
-        }
-
-        /// <summary>
-        /// Multiplies each element of the matrix by a scalar and places results into the result matrix.
-        /// </summary>
-        /// <param name="scalar">The scalar to multiply the matrix with.</param>
-        /// <param name="result">The matrix to multiply.</param>
-        /// <exception cref="ArgumentNullException">If the result matrix is <see langword="null" />.</exception> 
-        /// <exception cref="ArgumentException">If the result matrix's dimensions are not the same as this matrix.</exception>
-        public virtual void Multiply(double scalar, Matrix result)
-        {
-            if (result == null)
-            {
-                throw new ArgumentNullException("result");
-            }
-
-            if (result.RowCount != RowCount)
-            {
-                throw new ArgumentException("result", Resources.ArgumentMatrixSameRowDimension);
-            }
-
-            if (result.ColumnCount != ColumnCount)
-            {
-                throw new ArgumentException("result", Resources.ArgumentMatrixSameColumnDimension);
-            }
-
-            CopyTo(result);
-            result.Multiply(scalar);
-        }
-
         /// <summary>
         /// Adds another matrix to this matrix. The result will be written into this matrix.
         /// </summary>
@@ -119,39 +68,6 @@ namespace MathNet.Numerics.LinearAlgebra.Double
                 });
         }
 
-        /// <summary>
-        /// Adds two matrices together and returns the results.
-        /// </summary>
-        /// <remarks>This operator will allocate new memory for the result. It will
-        /// choose the representation of either <paramref name="leftSide"/> or <paramref name="rightSide"/> depending on which
-        /// is denser.</remarks>
-        /// <param name="leftSide">The left matrix to add.</param>
-        /// <param name="rightSide">The right matrix to add.</param>
-        /// <returns>The result of the addition.</returns>
-        /// <exception cref="ArgumentOutOfRangeException">If <paramref name="leftSide"/> and <paramref name="rightSide"/> don't have the same dimensions.</exception>
-        /// <exception cref="ArgumentNullException">If <paramref name="leftSide"/> or <paramref name="rightSide"/> is <see langword="null" />.</exception>
-        public static Matrix operator +(Matrix leftSide, Matrix rightSide)
-        {
-            if (rightSide == null)
-            {
-                throw new ArgumentNullException("rightSide");
-            }
-
-            if (leftSide == null)
-            {
-                throw new ArgumentNullException("leftSide");
-            }
-
-            if (leftSide.RowCount != rightSide.RowCount || leftSide.ColumnCount != rightSide.ColumnCount)
-            {
-                throw new ArgumentOutOfRangeException(Resources.ArgumentMatrixDimensions);
-            }
-
-            Matrix ret = leftSide.Clone();
-            ret.Add(rightSide);
-            return ret;
-        }
-
         /// <summary>
         /// Subtracts another matrix from this matrix. The result will be written into this matrix.
         /// </summary>
@@ -181,38 +97,55 @@ namespace MathNet.Numerics.LinearAlgebra.Double
                     }
                 });
         }
+        /// <summary>
+        /// Multiplies each element of this matrix with a scalar.
+        /// </summary>
+        /// <param name="scalar">The scalar to multiply with.</param>
+        public virtual void Multiply(double scalar)
+        {
+            if (Precision.AlmostEqualInDecimalPlaces(1.0, scalar, 15))
+            {
+                return;
+            }
+
+            Parallel.For(
+                0,
+                RowCount,
+                i =>
+                {
+                    for (int j = 0; j < ColumnCount; j++)
+                    {
+                        At(i, j, At(i, j) * scalar);
+                    }
+                });
+        }
 
         /// <summary>
-        /// Subtracts two matrices together and returns the results.
+        /// Multiplies each element of the matrix by a scalar and places results into the result matrix.
         /// </summary>
-        /// <remarks>This operator will allocate new memory for the result. It will
-        /// choose the representation of either <paramref name="leftSide"/> or <paramref name="rightSide"/> depending on which
-        /// is denser.</remarks>
-        /// <param name="leftSide">The left matrix to subtract.</param>
-        /// <param name="rightSide">The right matrix to subtract.</param>
-        /// <returns>The result of the addition.</returns>
-        /// <exception cref="ArgumentOutOfRangeException">If <paramref name="leftSide"/> and <paramref name="rightSide"/> don't have the same dimensions.</exception>
-        /// <exception cref="ArgumentNullException">If <paramref name="leftSide"/> or <paramref name="rightSide"/> is <see langword="null" />.</exception>
-        public static Matrix operator -(Matrix leftSide, Matrix rightSide)
+        /// <param name="scalar">The scalar to multiply the matrix with.</param>
+        /// <param name="result">The matrix to multiply.</param>
+        /// <exception cref="ArgumentNullException">If the result matrix is <see langword="null" />.</exception> 
+        /// <exception cref="ArgumentException">If the result matrix's dimensions are not the same as this matrix.</exception>
+        public virtual void Multiply(double scalar, Matrix result)
         {
-            if (rightSide == null)
+            if (result == null)
             {
-                throw new ArgumentNullException("rightSide");
+                throw new ArgumentNullException("result");
             }
 
-            if (leftSide == null)
+            if (result.RowCount != RowCount)
             {
-                throw new ArgumentNullException("leftSide");
+                throw new ArgumentException("result", Resources.ArgumentMatrixSameRowDimension);
             }
 
-            if (leftSide.RowCount != rightSide.RowCount || leftSide.ColumnCount != rightSide.ColumnCount)
+            if (result.ColumnCount != ColumnCount)
             {
-                throw new ArgumentOutOfRangeException(Resources.ArgumentMatrixDimensions);
+                throw new ArgumentException("result", Resources.ArgumentMatrixSameColumnDimension);
             }
 
-            Matrix ret = leftSide.Clone();
-            ret.Subtract(rightSide);
-            return ret;
+            CopyTo(result);
+            result.Multiply(scalar);
         }
 
         /// <summary>
@@ -295,6 +228,110 @@ namespace MathNet.Numerics.LinearAlgebra.Double
             return result;
         }
 
+        /// <summary>
+        /// Adds two matrices together and returns the results.
+        /// </summary>
+        /// <remarks>This operator will allocate new memory for the result. It will
+        /// choose the representation of either <paramref name="leftSide"/> or <paramref name="rightSide"/> depending on which
+        /// is denser.</remarks>
+        /// <param name="leftSide">The left matrix to add.</param>
+        /// <param name="rightSide">The right matrix to add.</param>
+        /// <returns>The result of the addition.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">If <paramref name="leftSide"/> and <paramref name="rightSide"/> don't have the same dimensions.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="leftSide"/> or <paramref name="rightSide"/> is <see langword="null" />.</exception>
+        public static Matrix operator +(Matrix leftSide, Matrix rightSide)
+        {
+            if (rightSide == null)
+            {
+                throw new ArgumentNullException("rightSide");
+            }
+
+            if (leftSide == null)
+            {
+                throw new ArgumentNullException("leftSide");
+            }
+
+            if (leftSide.RowCount != rightSide.RowCount || leftSide.ColumnCount != rightSide.ColumnCount)
+            {
+                throw new ArgumentOutOfRangeException(Resources.ArgumentMatrixDimensions);
+            }
+
+            Matrix ret = leftSide.Clone();
+            ret.Add(rightSide);
+            return ret;
+        }
+
+        /// <summary>
+        /// Subtracts two matrices together and returns the results.
+        /// </summary>
+        /// <remarks>This operator will allocate new memory for the result. It will
+        /// choose the representation of either <paramref name="leftSide"/> or <paramref name="rightSide"/> depending on which
+        /// is denser.</remarks>
+        /// <param name="leftSide">The left matrix to subtract.</param>
+        /// <param name="rightSide">The right matrix to subtract.</param>
+        /// <returns>The result of the addition.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">If <paramref name="leftSide"/> and <paramref name="rightSide"/> don't have the same dimensions.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="leftSide"/> or <paramref name="rightSide"/> is <see langword="null" />.</exception>
+        public static Matrix operator -(Matrix leftSide, Matrix rightSide)
+        {
+            if (rightSide == null)
+            {
+                throw new ArgumentNullException("rightSide");
+            }
+
+            if (leftSide == null)
+            {
+                throw new ArgumentNullException("leftSide");
+            }
+
+            if (leftSide.RowCount != rightSide.RowCount || leftSide.ColumnCount != rightSide.ColumnCount)
+            {
+                throw new ArgumentOutOfRangeException(Resources.ArgumentMatrixDimensions);
+            }
+
+            Matrix ret = leftSide.Clone();
+            ret.Subtract(rightSide);
+            return ret;
+        }
+
+        /// <summary>
+        /// Multiplies a <strong>Matrix</strong> by a constant and returns the result.
+        /// </summary>
+        /// <param name="leftSide">The matrix to multiply.</param>
+        /// <param name="rightSide">The constant to multiply the matrix by.</param>
+        /// <returns>The result of the multiplication.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="leftSide"/> is <see langword="null" />.</exception>
+        public static Matrix operator *(Matrix leftSide, double rightSide)
+        {
+            if (leftSide == null)
+            {
+                throw new ArgumentNullException("leftSide");
+            }
+
+            Matrix ret = leftSide.Clone();
+            ret.Multiply(rightSide);
+            return ret;
+        }
+
+        /// <summary>
+        /// Multiplies a <strong>Matrix</strong> by a constant and returns the result.
+        /// </summary>
+        /// <param name="leftSide">The matrix to multiply.</param>
+        /// <param name="rightSide">The constant to multiply the matrix by.</param>
+        /// <returns>The result of the multiplication.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="rightSide"/> is <see langword="null" />.</exception>
+        public static Matrix operator *(double leftSide, Matrix rightSide)
+        {
+            if (rightSide == null)
+            {
+                throw new ArgumentNullException("rightSide");
+            }
+
+            Matrix ret = rightSide.Clone();
+            ret.Multiply(leftSide);
+            return ret;
+        }
+
         /// <summary>
         /// Multiplies two matrices.
         /// </summary>

src/UnitTests/LinearAlgebraTests/Double/MatrixTests.Arithmetic.cs

@@ -28,6 +28,44 @@ namespace MathNet.Numerics.UnitTests.LinearAlgebraTests.Double
             }
         }
 
+        [Test]
+        [Row(0)]
+        [Row(1)]
+        [Row(2.2)]
+        [MultipleAsserts]
+        public void CanOperatorLeftMultiplyWithScalar(double scalar)
+        {
+            var matrix = testMatrices["Singular3x3"];
+            var clone = matrix * scalar;
+
+            for (int i = 0; i < matrix.RowCount; i++)
+            {
+                for (int j = 0; j < matrix.ColumnCount; j++)
+                {
+                    Assert.AreEqual(matrix[i, j] * scalar, clone[i, j]);
+                }
+            }
+        }
+
+        [Test]
+        [Row(0)]
+        [Row(1)]
+        [Row(2.2)]
+        [MultipleAsserts]
+        public void CanOperatorRightMultiplyWithScalar(double scalar)
+        {
+            var matrix = testMatrices["Singular3x3"];
+            var clone = matrix * scalar;
+
+            for (int i = 0; i < matrix.RowCount; i++)
+            {
+                for (int j = 0; j < matrix.ColumnCount; j++)
+                {
+                    Assert.AreEqual(matrix[i, j] * scalar, clone[i, j]);
+                }
+            }
+        }
+
         [Test]
         [Row(0)]
         [Row(1)]
@@ -75,10 +113,26 @@ namespace MathNet.Numerics.UnitTests.LinearAlgebraTests.Double
             matrix.Multiply(2.3, result);
         }
 
+        [Test]
+        [ExpectedException(typeof(ArgumentNullException))]
+        public void OperatorLeftMultiplyWithScalarFailsWhenMatrixIsNull()
+        {
+            Matrix matrix = null;
+            Matrix result = 2.3 * matrix;
+        }
+
+        [Test]
+        [ExpectedException(typeof(ArgumentNullException))]
+        public void OperatorRightMultiplyWithScalarFailsWhenMatrixIsNull()
+        {
+            Matrix matrix = null;
+            Matrix result = matrix * 2.3;
+        }
+
         [Test]
         [Row("Singular3x3", "Square3x3")]
         [Row("Singular4x4", "Square4x4")]
-        public void AddMatrix(string mtxA, string mtxB)
+        public void CanAddMatrix(string mtxA, string mtxB)
         {
             var A = testMatrices[mtxA];
             var B = testMatrices[mtxB];
@@ -178,7 +232,7 @@ namespace MathNet.Numerics.UnitTests.LinearAlgebraTests.Double
         [Test]
         [Row("Singular3x3", "Square3x3")]
         [Row("Singular4x4", "Square4x4")]
-        public void SubtractMatrix(string mtxA, string mtxB)
+        public void CanSubtractMatrix(string mtxA, string mtxB)
         {
             var A = testMatrices[mtxA];
             var B = testMatrices[mtxB];