Add new class: PackedStorageIndexerUpper

Signed-off-by: Alexander Karatarakis <alex@karatarakis.com>

src/Numerics/LinearAlgebra/Storage/Indexers/Static/PackedStorageIndexerUpper.cs

@@ -0,0 +1,88 @@
+namespace MathNet.Numerics.LinearAlgebra.Storage.Indexers.Static
+{
+    using System;
+
+    /// <summary>
+    ///  A class for managing indexing when using Packed Storage scheme, which is a column-Wise packing scheme for Symmetric, Hermitian or Triangular square matrices. 
+    ///  This variation provides indexes for storing the upper triangle of a matrix (row less than or equal to column).
+    /// </summary>
+    public class PackedStorageIndexerUpper : PackedStorageIndexer
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PackedStorageIndexerUpper"/> class.
+        /// </summary>
+        /// <param name="order">
+        /// The order of the matrix.
+        /// </param>
+        internal PackedStorageIndexerUpper(int order)
+            : base(order)
+        {
+        }
+
+        /// <summary>
+        ///   Gets the index of the given element.
+        /// </summary>
+        /// <param name = "row">
+        ///   The row of the element.
+        /// </param>
+        /// <param name = "column">
+        ///   The column of the element.
+        /// </param>
+        /// <remarks>
+        ///   This method is parameter checked. <see cref = "IndexOf(int,int)" /> and <see cref = "IndexOfDiagonal(int)" /> to get values without parameter checking.
+        /// </remarks>
+        public override int this[int row, int column]
+        {
+            get
+            {
+                if (row < 0 || row >= Order)
+                {
+                    throw new ArgumentOutOfRangeException("row");
+                }
+
+                if (column < 0 || column >= Order)
+                {
+                    throw new ArgumentOutOfRangeException("column");
+                }
+
+                if (row > column)
+                {
+                    throw new ArgumentException("Row must be less than or equal to column");
+                }
+
+                return IndexOf(row, column);
+            }
+        }
+
+        /// <summary>
+        /// Retrieves the index of the requested element without parameter checking. Row must be less than or equal to column.
+        /// </summary>
+        /// <param name="row">
+        /// The row of the element. 
+        /// </param>
+        /// <param name="column">
+        /// The column of the element. 
+        /// </param>
+        /// <returns>
+        /// The requested index. 
+        /// </returns>
+        public override int IndexOf(int row, int column)
+        {
+            return row + ((column * (column + 1)) / 2);
+        }
+
+        /// <summary>
+        /// Retrieves the index of the requested diagonal element without parameter checking.
+        /// </summary>
+        /// <param name="row">
+        /// The row=column of the diagonal element. 
+        /// </param>
+        /// <returns>
+        /// The requested index. 
+        /// </returns>
+        public override int IndexOfDiagonal(int row)
+        {
+            return (row * (row + 3)) / 2;
+        }
+    }
+}

src/Numerics/Numerics.csproj

@@ -143,6 +143,7 @@
     <Compile Include="LinearAlgebra\Storage\DenseVectorStorage.cs" />
     <Compile Include="LinearAlgebra\Storage\Indexers\IStorageIndexer.cs" />
     <Compile Include="LinearAlgebra\Storage\Indexers\Static\PackedStorageIndexer.cs" />
+    <Compile Include="LinearAlgebra\Storage\Indexers\Static\PackedStorageIndexerUpper.cs" />
     <Compile Include="LinearAlgebra\Storage\Indexers\Static\StaticStorageIndexer.cs" />
     <Compile Include="LinearAlgebra\Storage\MatrixStorage.Validation.cs" />
     <Compile Include="LinearAlgebra\Complex32\ExtensionMethods.cs" />