Null elements

NullElements/.editorconfig

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+[*.cs]
+
+# SA1600: Elements should be documented
+dotnet_diagnostic.SA1600.severity = none

NullElements/NullElements.Tests/NullElements.Tests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <LangVersion>latest</LangVersion>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Remove="stylecop.json" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <AdditionalFiles Include="stylecop.json" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.2" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="NUnit" Version="4.2.2" />
+    <PackageReference Include="NUnit.Analyzers" Version="4.4.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.6.0" />
+    <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.556">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\NullElements\NullElements.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="NUnit.Framework" />
+  </ItemGroup>
+
+</Project>

NullElements/NullElements.Tests/NullElementsTests.cs

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+// <copyright file="NullElementsTests.cs" company="Kalinin Andrew">
+// Copyright (c) Kalinin Andrew. All rights reserved.
+// </copyright>
+
+namespace NullElements.Tests
+{
+    public class NullElementsTests
+    {
+        [Test]
+        public void Add_NumberToEmptyList_ShouldIncreaseCountByOne()
+        {
+            var testList = new MyList<int>();
+            testList.Add(5);
+
+            Assert.That(testList.Count, Is.EqualTo(1));
+        }
+
+        [Test]
+        public void Add_Overflow_ShouldDoubleInternalArraySize()
+        {
+            var testList = new MyList<int>();
+            var initialCapacity = 10;
+            for (int i = 0; i < initialCapacity + 1; ++i)
+            {
+                testList.Add(i);
+            }
+
+            Assert.That(testList.Count, Is.EqualTo(11));
+        }
+
+        [Test]
+        public void GetEnumerator_ValidData_ShouldIterateInCorrectOrder()
+        {
+            var testList = new MyList<int>();
+            testList.Add(1);
+            testList.Add(2);
+
+            var result = new System.Collections.Generic.List<int>();
+            foreach (var item in testList)
+            {
+                result.Add(item);
+            }
+
+            Assert.That(result, Is.EqualTo(new[] { 1, 2 }));
+        }
+
+        [Test]
+        public void GetEnumerator_WhenListIsEmpty_ShouldNotIterate()
+        {
+            var testList = new MyList<string>();
+
+            var iterations = 0;
+            foreach (var item in testList)
+            {
+                iterations++;
+            }
+
+            Assert.That(iterations, Is.EqualTo(0));
+        }
+
+        [Test]
+        public void CountNulls_String_ShouldReturnCorrectCount()
+        {
+            var testList = new MyList<string>();
+            testList.Add("hello");
+            testList.Add(null);
+            testList.Add(string.Empty);
+            testList.Add("world");
+
+            var result = Counter.CountNulls(testList, new StringNullChecker());
+
+            Assert.That(result, Is.EqualTo(2));
+        }
+
+        [Test]
+        public void CountNulls_Int_ShouldReturnCorrectCountZeros()
+        {
+            var testList = new MyList<int>();
+            testList.Add(0);
+            testList.Add(1);
+            testList.Add(0);
+
+            var result = Counter.CountNulls(testList, new IntNullChecker());
+
+            Assert.That(result, Is.EqualTo(2));
+        }
+
+        [Test]
+        public void CountNulls_WhenIntListIsEmpty_ShouldReturnZero()
+        {
+            var testList = new MyList<int>();
+
+            var result = Counter.CountNulls(testList, new IntNullChecker());
+
+            Assert.That(result, Is.EqualTo(0));
+        }
+
+        [Test]
+        public void CountNulls_WhenStringListIsEmpty_ShouldReturnZero()
+        {
+            var testList = new MyList<string>();
+
+            var result = Counter.CountNulls(testList, new StringNullChecker());
+
+            Assert.That(result, Is.EqualTo(0));
+        }
+    }
+}

NullElements/NullElements.Tests/stylecop.json

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+{
+  // ACTION REQUIRED: This file was automatically added to your project, but it
+  // will not take effect until additional steps are taken to enable it. See the
+  // following page for additional information:
+  //
+  // https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/EnableConfiguration.md
+
+  "$schema": "https://raw.githubusercontent.com/DotNetAnalyzers/StyleCopAnalyzers/master/StyleCop.Analyzers/StyleCop.Analyzers/Settings/stylecop.schema.json",
+  "settings": {
+    "documentationRules": {
+      "companyName": "Kalinin Andrew",
+      "copyrightText": "Copyright (c) {companyName}. All rights reserved."
+    }
+  }
+}

NullElements/NullElements.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.13.35806.99 d17.13
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NullElements", "NullElements\NullElements.csproj", "{2BA0FF1E-3004-4D5F-A36F-9E7122EE2145}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NullElements.Tests", "NullElements.Tests\NullElements.Tests.csproj", "{1AE28732-923A-4DDE-BE64-28751F09CC28}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{36D591C7-65C7-A0D1-1CBC-10CDE441BDC8}"
+	ProjectSection(SolutionItems) = preProject
+		.editorconfig = .editorconfig
+	EndProjectSection
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{2BA0FF1E-3004-4D5F-A36F-9E7122EE2145}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2BA0FF1E-3004-4D5F-A36F-9E7122EE2145}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2BA0FF1E-3004-4D5F-A36F-9E7122EE2145}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2BA0FF1E-3004-4D5F-A36F-9E7122EE2145}.Release|Any CPU.Build.0 = Release|Any CPU
+		{1AE28732-923A-4DDE-BE64-28751F09CC28}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{1AE28732-923A-4DDE-BE64-28751F09CC28}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{1AE28732-923A-4DDE-BE64-28751F09CC28}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{1AE28732-923A-4DDE-BE64-28751F09CC28}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {979D0980-DB24-4BC7-909D-644F6A87E14F}
+	EndGlobalSection
+EndGlobal

NullElements/NullElements/Counter.cs

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+// <copyright file="Counter.cs" company="Kalinin Andrew">
+// Copyright (c) Kalinin Andrew. All rights reserved.
+// </copyright>
+
+namespace NullElements
+{
+    /// <summary>
+    /// Provides utility methods for working with collections.
+    /// </summary>
+    public static class Counter
+    {
+        /// <summary>
+        /// Counts elements that match null-equivalent conditions.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in the list.</typeparam>
+        /// <param name="list">The collection to inspect.</param>
+        /// <param name="checker">The null-equivalence checker implementation.</param>
+        /// <returns>The number of null-equivalent elements.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when list or checker is null.</
+        public static int CountNulls<T>(MyList<T> list, ICheckNulls<T> checker)
+        {
+            if (list == null)
+            {
+                throw new ArgumentNullException(nameof(list));
+            }
+
+            if (checker == null)
+            {
+                throw new ArgumentNullException(nameof(checker));
+            }
+
+            int count = 0;
+
+            foreach (var item in list)
+            {
+                if (checker.IsNull(item))
+                {
+                    count++;
+                }
+            }
+
+            return count;
+        }
+    }
+}

NullElements/NullElements/ICheckNulls.cs

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+// <copyright file="ICheckNulls.cs" company="Kalinin Andrew">
+// Copyright (c) Kalinin Andrew. All rights reserved.
+// </copyright>
+
+namespace NullElements
+{
+    /// <summary>
+    /// Interface for checking if elements meet null-equivalent conditions.
+    /// </summary>
+    /// <typeparam name="T">The type of elements to check.</typeparam>
+    public interface ICheckNulls<T>
+    {
+        /// <summary>
+        /// Determines if an item should be considered null-equivalent.
+        /// </summary>
+        /// <param name="item">The item to check.</param>
+        /// <returns>True if the item is considered null-equivalent, otherwise False.</returns>
+        bool IsNull(T item);
+    }
+}

NullElements/NullElements/IntNullChecker.cs

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+// <copyright file="IntNullChecker.cs" company="Kalinin Andrew">
+// Copyright (c) Kalinin Andrew. All rights reserved.
+// </copyright>
+
+namespace NullElements
+{
+    /// <summary>
+    /// Null-equivalence checker for integer values.
+    /// </summary>
+    public class IntNullChecker : ICheckNulls<int>
+    {
+        /// <summary>
+        /// Determines if an integer is zero.
+        /// </summary>
+        /// <param name="item">The integer to check.</param>
+        /// <returns>True if the value is zero, otherwise False.</returns>
+        public bool IsNull(int item) => item == 0;
+    }
+}

NullElements/NullElements/MyList.cs

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+// <copyright file="MyList.cs" company="Kalinin Andrew">
+// Copyright (c) Kalinin Andrew. All rights reserved.
+// </copyright>
+
+using System.Collections;
+
+/// <summary>
+/// Custom generic list implementation with dynamic resizing.
+/// </summary>
+/// <typeparam name="T">The type of elements in the list.</typeparam>
+public class MyList<T> : IEnumerable<T>
+{
+    private T[] items;
+
+    private int count;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="MyList{T}"/> class.
+    /// </summary>
+    public MyList()
+    {
+        this.items = new T[4];
+        this.count = 0;
+    }
+
+    public int Count => this.count;
+
+    /// <summary>
+    /// Adds an item to the end of the list.
+    /// </summary>
+    /// <param name="item">The item to add.</param>
+    public void Add(T item)
+    {
+        if (this.count == this.items.Length)
+        {
+            Array.Resize(ref this.items, this.items.Length == 0 ? 10 : this.items.Length * 2);
+        }
+
+        this.items[this.count] = item;
+        this.count++;
+    }
+
+    /// <summary>
+    /// Returns an enumerator that iterates through the collection.
+    /// </summary>
+    /// <returns>An enumerator for the list.</returns>
+    public IEnumerator<T> GetEnumerator()
+    {
+        for (int i = 0; i < this.count; ++i)
+        {
+            yield return this.items[i];
+        }
+    }
+
+    IEnumerator IEnumerable.GetEnumerator()
+    {
+        return this.GetEnumerator();
+    }
+}

NullElements/NullElements/NullElements.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Remove="stylecop.json" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <AdditionalFiles Include="stylecop.json" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.556">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+</Project>

NullElements/NullElements/Program.cs

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+// <copyright file="Program.cs" company="Kalinin Andrew">
+// Copyright (c) Kalinin Andrew. All rights reserved.
+// </copyright>
+
+using NullElements;
+
+var intList = new MyList<int>();
+intList.Add(0);
+intList.Add(0);
+intList.Add(0);
+intList.Add(0);
+
+Console.WriteLine(Counter.CountNulls(intList, new IntNullChecker()));