From aa221977da1a500a8a1b48a78f51e5a806380885 Mon Sep 17 00:00:00 2001
From: Christoph Ruegg <git@cdrnet.ch>
Date: Tue, 17 Jun 2014 01:02:38 +0200
Subject: [PATCH] Distance: fix bug in Hamming distance that skipped the head
 pair #220

---
 src/Numerics/Distance.cs       |  4 ++--
 src/UnitTests/DistanceTests.cs | 19 +++++++++++++++++++
 src/UnitTests/UnitTests.csproj |  1 +
 3 files changed, 22 insertions(+), 2 deletions(-)
 create mode 100644 src/UnitTests/DistanceTests.cs

diff --git a/src/Numerics/Distance.cs b/src/Numerics/Distance.cs
index 425c6152..05ddd6ff 100644
--- a/src/Numerics/Distance.cs
+++ b/src/Numerics/Distance.cs
@@ -351,7 +351,7 @@ namespace MathNet.Numerics
         {
             if (a.Length != b.Length) throw new ArgumentOutOfRangeException("b");
             int count = 0;
-            for (int i = 1; i < a.Length; i++)
+            for (int i = 0; i < a.Length; i++)
             {
                 if (a[i] != b[i])
                 {
@@ -368,7 +368,7 @@ namespace MathNet.Numerics
         {
             if (a.Length != b.Length) throw new ArgumentOutOfRangeException("b");
             int count = 0;
-            for (int i = 1; i < a.Length; i++)
+            for (int i = 0; i < a.Length; i++)
             {
                 if (a[i] != b[i])
                 {
diff --git a/src/UnitTests/DistanceTests.cs b/src/UnitTests/DistanceTests.cs
new file mode 100644
index 00000000..b18e80a6
--- /dev/null
+++ b/src/UnitTests/DistanceTests.cs
@@ -0,0 +1,19 @@
+using NUnit.Framework;
+
+namespace MathNet.Numerics.UnitTests
+{
+    [TestFixture]
+    public class DistanceTests
+    {
+        [Test]
+        public void Hamming()
+        {
+            Assert.That(Distance.Hamming(new[] { 0.0, 0.0 }, new[] { 0.0, 0.0 }), Is.EqualTo(0.0));
+            Assert.That(Distance.Hamming(new[] { 1.0, 0.0 }, new[] { 1.0, 0.0 }), Is.EqualTo(0.0));
+            Assert.That(Distance.Hamming(new[] { 0.0, 0.0 }, new[] { 1.0, 0.0 }), Is.EqualTo(1.0));
+            Assert.That(Distance.Hamming(new[] { 0.0, 0.0 }, new[] { 0.0, 1.0 }), Is.EqualTo(1.0));
+            Assert.That(Distance.Hamming(new[] { 0.0, 0.0 }, new[] { 1.0, 1.0 }), Is.EqualTo(2.0));
+            Assert.That(Distance.Hamming(new[] { 1.0, 0.0 }, new[] { 0.0, 1.0 }), Is.EqualTo(2.0));
+        }
+    }
+}
diff --git a/src/UnitTests/UnitTests.csproj b/src/UnitTests/UnitTests.csproj
index cd1e2369..069ba696 100644
--- a/src/UnitTests/UnitTests.csproj
+++ b/src/UnitTests/UnitTests.csproj
@@ -85,6 +85,7 @@
     <Compile Include="ComplexTests\Complex32Test.TextHandling.cs" />
     <Compile Include="ComplexTests\ComplexTest.cs" />
     <Compile Include="ComplexTests\ComplexTest.TextHandling.cs" />
+    <Compile Include="DistanceTests.cs" />
     <Compile Include="DistributionTests\CommonDistributionTests.cs" />
     <Compile Include="DistributionTests\Continuous\BetaTests.cs" />
     <Compile Include="DistributionTests\Continuous\CauchyTests.cs" />