Add new abstract class: PackedStorageIndexer

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

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

@@ -0,0 +1,50 @@
+namespace MathNet.Numerics.LinearAlgebra.Storage.Indexers.Static
+{
+    using System;
+    using Properties;
+
+    /// <summary>
+    /// A class for managing indexing when using Packed Storage indexer, which is a column-major packing scheme for dense Symmetric, Hermitian or Triangular square matrices.
+    /// </summary>
+    public abstract class PackedStorageIndexer : StaticStorageIndexer
+    {
+        /// <summary>
+        ///   Number of rows or columns.
+        /// </summary>
+        protected readonly int Order;
+
+        /// <summary>
+        ///   Length of the stored data. 
+        /// </summary>
+        private readonly int _dataLength;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PackedStorageIndexer"/> class.
+        /// </summary>
+        /// <param name="order">
+        /// The order of the matrix.
+        /// </param>
+        /// <exception cref="ArgumentOutOfRangeException"><c></c> is out of range.</exception>
+        protected PackedStorageIndexer(int order)
+        {
+            if (order <= 0)
+            {
+                throw new ArgumentOutOfRangeException(Resources.MatrixRowsOrColumnsMustBePositive);
+            }
+
+            Order = order;
+            _dataLength = order * (order + 1) / 2;
+        }
+
+        /// <summary>
+        /// Gets the length of the stored data. 
+        /// </summary>
+        public override int DataLength
+        {
+            get
+            {
+                return _dataLength;
+            }
+        }
+    }
+}

src/Numerics/Numerics.csproj

@@ -142,6 +142,7 @@
     <Compile Include="Distributions\Multivariate\Wishart.cs" />
     <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\StaticStorageIndexer.cs" />
     <Compile Include="LinearAlgebra\Storage\MatrixStorage.Validation.cs" />
     <Compile Include="LinearAlgebra\Complex32\ExtensionMethods.cs" />