From 478991b870240dcec9e1fb8daafb9a963e46f03a Mon Sep 17 00:00:00 2001
From: Marcus Cuda <marcus@cuda.org>
Date: Thu, 20 Aug 2009 15:20:12 +0800
Subject: [PATCH] vector: added equals and gethashcode methods

Signed-off-by: Marcus Cuda <marcus@cuda.net>
---
 src/Numerics/LinearAlgebra/Double/Matrix.cs   | 37 ++++++++++++
 src/Numerics/LinearAlgebra/Double/Vector.cs   | 57 +++++++++++++++----
 .../LinearAlgebraTests/Double/VectorTests.cs  | 22 +++++++
 3 files changed, 104 insertions(+), 12 deletions(-)

diff --git a/src/Numerics/LinearAlgebra/Double/Matrix.cs b/src/Numerics/LinearAlgebra/Double/Matrix.cs
index 1699e284..7bb13c27 100644
--- a/src/Numerics/LinearAlgebra/Double/Matrix.cs
+++ b/src/Numerics/LinearAlgebra/Double/Matrix.cs
@@ -341,5 +341,42 @@ namespace MathNet.Numerics.LinearAlgebra.Double
                 throw new ArgumentOutOfRangeException("column");
             }
         }
+
+        #region System.Object overrides
+
+        /// <summary>
+        /// Determines whether the specified <see cref="System.Object"/> is equal to this instance.
+        /// </summary>
+        /// <param name="obj">The <see cref="System.Object"/> to compare with this instance.</param>
+        /// <returns>
+        ///     <c>true</c> if the specified <see cref="System.Object"/> is equal to this instance; otherwise, <c>false</c>.
+        /// </returns>
+        public override bool Equals(object obj)
+        {
+            return Equals(obj as Matrix);
+        }
+
+        /// <summary>
+        /// Returns a hash code for this instance.
+        /// </summary>
+        /// <returns>
+        /// A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table. 
+        /// </returns>
+        public override int GetHashCode()
+        {
+            var hashNum = Math.Min(RowCount * ColumnCount, 25);
+            long hash = 0;
+            for (var i = 0; i < hashNum; i++)
+            {
+                var col = i % ColumnCount;
+                var row = (i - col) / RowCount;
+
+                hash ^= BitConverter.DoubleToInt64Bits(this[row, col]);
+            }
+
+            return BitConverter.ToInt32(BitConverter.GetBytes(hash), 4);
+        }
+
+        #endregion
     }
 }
\ No newline at end of file
diff --git a/src/Numerics/LinearAlgebra/Double/Vector.cs b/src/Numerics/LinearAlgebra/Double/Vector.cs
index 9c7c2397..24e60d19 100644
--- a/src/Numerics/LinearAlgebra/Double/Vector.cs
+++ b/src/Numerics/LinearAlgebra/Double/Vector.cs
@@ -829,17 +829,6 @@ namespace MathNet.Numerics.LinearAlgebra.Double
             }
         }
 
-        /// <summary>
-        /// Returns a <see cref="System.String"/> that represents this instance.
-        /// </summary>
-        /// <returns>
-        /// A <see cref="System.String"/> that represents this instance.
-        /// </returns>
-        public override string ToString()
-        {
-            return ToString(null, null);
-        }
-
         #endregion
 
         #region Implemented Interfaces
@@ -930,7 +919,7 @@ namespace MathNet.Numerics.LinearAlgebra.Double
             // If all else fails, perform element wise comparison.
             for (var index = 0; index < Count; index++)
             {
-                if (this[index] != other[index])
+                if (!this[index].AlmostEqual(other[index]))
                 {
                     return false;
                 }
@@ -973,5 +962,49 @@ namespace MathNet.Numerics.LinearAlgebra.Double
         #endregion
 
         #endregion
+
+        #region System.Object overrides
+
+        /// <summary>
+        /// Determines whether the specified <see cref="System.Object"/> is equal to this instance.
+        /// </summary>
+        /// <param name="obj">The <see cref="System.Object"/> to compare with this instance.</param>
+        /// <returns>
+        ///     <c>true</c> if the specified <see cref="System.Object"/> is equal to this instance; otherwise, <c>false</c>.
+        /// </returns>
+        public override bool Equals(object obj)
+        {
+            return Equals(obj as Vector);
+        }
+
+        /// <summary>
+        /// Returns a hash code for this instance.
+        /// </summary>
+        /// <returns>
+        /// A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table. 
+        /// </returns>
+        public override int GetHashCode()
+        {
+            var hashNum = Math.Min(Count, 20);
+            long hash = 0;
+            for (var i = 0; i < hashNum; i++)
+            {
+                hash ^= BitConverter.DoubleToInt64Bits(this[i]);
+            }
+
+            return BitConverter.ToInt32(BitConverter.GetBytes(hash), 4);
+        }
+
+        /// <summary>
+        /// Returns a <see cref="System.String"/> that represents this instance.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="System.String"/> that represents this instance.
+        /// </returns>
+        public override string ToString()
+        {
+            return ToString(null, null);
+        }
+        #endregion
     }
 }
\ No newline at end of file
diff --git a/src/UnitTests/LinearAlgebraTests/Double/VectorTests.cs b/src/UnitTests/LinearAlgebraTests/Double/VectorTests.cs
index 1a95836c..546ed2e5 100644
--- a/src/UnitTests/LinearAlgebraTests/Double/VectorTests.cs
+++ b/src/UnitTests/LinearAlgebraTests/Double/VectorTests.cs
@@ -157,6 +157,28 @@ namespace MathNet.Numerics.UnitTests.LinearAlgebraTests.Double
             Assert.Throws<ArgumentException>(() => CreateVector(0));
         }
 
+        [Test]
+        public void TestingForEqualityWithNonVectorReturnsFalse()
+        {
+            var vector = CreateVector(_data);
+            Assert.IsFalse(vector.Equals(2));
+        }
+
+        [Test]
+        public void CanTestForEqualityUsingObjectEquals()
+        {
+            var vector1 = CreateVector(_data);
+            var vector2 = CreateVector(_data);
+            Assert.IsTrue(vector1.Equals((object)vector2));
+        }
+
+        [Test]
+        public void VectorGetHashCode()
+        {
+            var vector = CreateVector(new double[] { 1, 2, 3, 4 });
+            Assert.AreEqual(2145910784, vector.GetHashCode());
+        }
+        
         protected abstract Vector CreateVector(int size);
 
         protected abstract Vector CreateVector(IList<double> data);