jube-fork/Accord.Math/Comparers/ElementComparer.cs

// Accord Math Library
// The Accord.NET Framework
// http://accord-framework.net
//
// Copyright © César Souza, 2009-2017
// cesarsouza at gmail.com
//
//    This library is free software; you can redistribute it and/or
//    modify it under the terms of the GNU Lesser General Public
//    License as published by the Free Software Foundation; either
//    version 2.1 of the License, or (at your option) any later version.
//
//    This library is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//    Lesser General Public License for more details.
//
//    You should have received a copy of the GNU Lesser General Public
//    License along with this library; if not, write to the Free Software
//    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
//

namespace Accord.Math.Comparers
{
    using System.Collections.Generic;
    using System;

    /// <summary>
    ///   Element-at-position comparer.
    /// </summary>
    /// 
    /// <remarks>
    ///   This class compares arrays by checking the value
    ///   of a particular element at a given array index.
    /// </remarks>
    /// 
    /// <example>
    /// <code>
    ///   // We sort the arrays according to the 
    ///   // elements at their second column.
    ///   
    ///   double[][] values =
    ///   {   //                 v
    ///       new double[] {  0, 3, 0 },
    ///       new double[] {  0, 4, 1 },
    ///       new double[] { -1, 1, 1 },
    ///       new double[] { -1, 5, 4 },
    ///       new double[] { -2, 2, 6 },
    ///   };
    ///   
    ///   // Sort the array considering only the second column
    ///   Array.Sort(values, new ElementComparer() { Index = 1 });
    ///   
    ///   // The result will be
    ///   double[][] result =
    ///   {
    ///       new double[] { -1, 1, 1 },
    ///       new double[] { -2, 2, 6 },
    ///       new double[] {  0, 3, 0 },
    ///       new double[] {  0, 4, 1 },
    ///       new double[] { -1, 5, 4 },
    ///   };
    /// </code>
    /// </example>
    /// 
    /// <seealso cref="ElementComparer{T}"/>
    /// <seealso cref="ArrayComparer{T}"/>
    /// <seealso cref="GeneralComparer"/>
    /// <seealso cref="CustomComparer{T}"/>
    /// 
    public class ElementComparer : ElementComparer<double>
    {
    }

    /// <summary>
    ///   Element-at-position comparer.
    /// </summary>
    /// 
    /// <remarks>
    ///   This class compares arrays by checking the value
    ///   of a particular element at a given array index.
    /// </remarks>
    /// 
    /// <example>
    /// <code>
    ///   // We sort the arrays according to the 
    ///   // elements at their second column.
    ///   
    ///   double[][] values =
    ///   {   //                 v
    ///       new double[] {  0, 3, 0 },
    ///       new double[] {  0, 4, 1 },
    ///       new double[] { -1, 1, 1 },
    ///       new double[] { -1, 5, 4 },
    ///       new double[] { -2, 2, 6 },
    ///   };
    ///   
    ///   // Sort the array considering only the second column
    ///   Array.Sort(values, new ElementComparer() { Index = 1 });
    ///   
    ///   // The result will be
    ///   double[][] result =
    ///   {
    ///       new double[] { -1, 1, 1 },
    ///       new double[] { -2, 2, 6 },
    ///       new double[] {  0, 3, 0 },
    ///       new double[] {  0, 4, 1 },
    ///       new double[] { -1, 5, 4 },
    ///   };
    /// </code>
    /// </example>
    /// 
    /// <seealso cref="ElementComparer"/>
    /// <seealso cref="ArrayComparer{T}"/>
    /// <seealso cref="GeneralComparer"/>
    /// <seealso cref="CustomComparer{T}"/>
    /// 
    public class ElementComparer<T> : IComparer<T[]>, IEqualityComparer<T[]>
        where T : IComparable, IEquatable<T>
    {
        /// <summary>
        ///   Gets or sets the element index to compare.
        /// </summary>
        /// 
        public int Index { get; set; }

        /// <summary>
        ///   Compares two objects and returns a value indicating 
        ///   whether one is less than, equal to, or greater than the other.
        /// </summary>
        /// 
        /// <param name="x">The first object to compare.</param>
        /// <param name="y">The second object to compare.</param>
        /// 
        public int Compare(T[] x, T[] y)
        {
            return x[Index].CompareTo(y[Index]);
        }

        /// <summary>
        ///   Determines whether two instances are equal.
        /// </summary>
        /// 
        /// <param name="x">The first object to compare.</param>
        /// <param name="y">The second object to compare.</param>
        /// 
        /// <returns>
        ///   <c>true</c> if the specified object is equal to the other; otherwise, <c>false</c>.
        /// </returns>
        ///   
        public bool Equals(T[] x, T[] y)
        {
            return x[Index].Equals(y[Index]);
        }

        /// <summary>
        ///   Returns a hash code for a given instance.
        /// </summary>
        /// 
        /// <param name="obj">The instance.</param>
        /// 
        /// <returns>
        ///   A hash code for the instance, suitable for use
        ///   in hashing algorithms and data structures like a hash table. 
        /// </returns>
        /// 
        public int GetHashCode(T[] obj)
        {
            return obj[Index].GetHashCode();
        }

    }
}