List<T> compatibility methods implemented. Unit tests extended. README.md updated.

README.md

@@ -138,10 +138,10 @@
 		1. ✅ `Span<T>`
 		1. ✅ `T[]`
 	1. ✅ Release 0.0.5
-	1. 👉 Implement `List<T>` compatibility pack in `RecyclableList<T>`
+	1. ✅ Implement `List<T>` compatibility pack in `RecyclableList<T>`
-	1. 🅿️ Overflow review
+	1. 👉 Overflow review
 		1. 🅿️ Add type casting to `long` for `<<` & `>>` operations, where required
-		1. 🅿️ Make type castings `checked`
+		1. 🅿️ Make type castings `checked`, where required
 	1. 🅿️ Release 0.0.6
 	1. 🅿️ Implement `List<T>` compatibility pack in `RecyclableLongList<T>`
 	1. 🅿️ Port `RecyclableLongList<T>` optimizations to `RecyclableList<T>`
@@ -198,6 +198,12 @@
 	1. 🅿️ Pools
 	1. 🅿️ Multi-threading
 	1. 🅿️ Add comparison tests vs `T[]` / `List<T>` equivalents
+	1. 🅿️ Add test cases for indexes beyond items count
+	1. 🅿️ Cover border cases
+		1. 🅿️ Non-existing items in `.Contains...()`, `.Exists...()`, `.Find...()`, `.IndexOf...()`, `.Last...()`
+		1. 🅿️ Duplicated items in `.Contains...()`, `.Exists...()`, `.Find...()`, `.IndexOf...()`, `.Last...()`
+		1. 🅿️ Append test data in reversed order in `.AddRange()`, `.InsertRange()` and similar tests
+		1. 🅿️ Switch tests to use Source / Target data variants in `.AddRange()`, `.InsertRange()` and similar tests
 1. 🅿️ Cleanup
 	1. 🅿️ Replace `LastBlockWithData` property with `_lastBlockWithData` field
 	1. 🅿️ Replace all internal properties refs with fields, where possible

Recyclable.Collections.Benchmarks/Benchmarks/BinarySearch_BestAndWorstCases.cs

@@ -0,0 +1,65 @@
+namespace Recyclable.Collections.Benchmarks
+{
+	public partial class RecyclableCollectionsBenchmarks
+	{
+		public void Array_BinarySearch_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjects;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(Array.BinarySearch(list, data[i]));
+				DoNothing(Array.BinarySearch(list, data[^(i + 1)]));
+			}
+		}
+
+		public void List_BinarySearch_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.BinarySearch(data[i]));
+				DoNothing(list.BinarySearch(data[^(i + 1)]));
+			}
+		}
+
+		public void PooledList_BinarySearch_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsPooledList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.BinarySearch(data[i]));
+				DoNothing(list.BinarySearch(data[^(i + 1)]));
+			}
+		}
+
+		public void RecyclableList_BinarySearch_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsRecyclableList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.BinarySearch(data[i]));
+				DoNothing(list.BinarySearch(data[^(i + 1)]));
+			}
+		}
+
+		// public void RecyclableLongList_BinarySearch_BestAndWorstCases()
+		// {
+		// 	var data = TestObjects;
+		// 	var list = TestObjectsAsRecyclableLongList;
+		// 	var dataCount = TestObjectCountForSlowMethods;
+		// 	for (var i = 0; i < dataCount; i++)
+		// 	{
+		// 		DoNothing(list.BinarySearch(data[i]));
+		// 		DoNothing(list.BinarySearch(data[^(i + 1)]));
+		// 	}
+		// }
+	}
+}

Recyclable.Collections.Benchmarks/Benchmarks/ConvertAll.cs

@@ -0,0 +1,48 @@
+namespace Recyclable.Collections.Benchmarks
+{
+	public partial class RecyclableCollectionsBenchmarks
+	{
+		public void Array_ConvertAll()
+		{
+			var data = TestObjects;
+			var list = TestObjects;
+			var dataCount = TestObjectCountForSlowMethods;
+			DoNothing(Array.ConvertAll(list, static (item) => (long) item));
+		}
+
+		public void List_ConvertAll()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsList;
+			var dataCount = TestObjectCountForSlowMethods;
+			DoNothing(list.ConvertAll(static (item) => (long)item));
+		}
+
+		public void PooledList_ConvertAll()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsPooledList;
+			var dataCount = TestObjectCountForSlowMethods;
+			using var converted = list.ConvertAll(static (item) => (long)item);
+			DoNothing(converted);
+		}
+
+		public void RecyclableList_ConvertAll()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsRecyclableList;
+			var dataCount = TestObjectCountForSlowMethods;
+			using RecyclableList<long> converted = list.ConvertAll(static (item) => (long)item);
+			DoNothing(converted);
+		}
+
+		// public void RecyclableLongList_ConvertAll()
+		// {
+		// 	var data = TestObjects;
+		// 	var list = TestObjectsAsRecyclableLongList;
+		// 	var dataCount = TestObjectCountForSlowMethods;
+		// 	using RecyclableList<long> converted = list.ConvertAll(static (item) => (long)item);
+		// 	DoNothing(converted);
+		// }
+	}
+}

Recyclable.Collections.Benchmarks/Benchmarks/Exists_BestAndWorstCases.cs

@@ -0,0 +1,65 @@
+namespace Recyclable.Collections.Benchmarks
+{
+	public partial class RecyclableCollectionsBenchmarks
+	{
+		public void Array_Exists_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjects;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(Array.Exists(list, (x) => x == data[i]));
+				DoNothing(Array.Exists(list, (x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void List_Exists_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.Exists((x) => x == data[i]));
+				DoNothing(list.Exists((x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void PooledList_Exists_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsPooledList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.Exists((x) => x == data[i]));
+				DoNothing(list.Exists((x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void RecyclableList_Exists_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsRecyclableList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.Exists((x) => x == data[i]));
+				DoNothing(list.Exists((x) => x == data[^(i + 1)]));
+			}
+		}
+
+		// public void RecyclableLongList_Exists_BestAndWorstCases()
+		// {
+		// 	var data = TestObjects;
+		// 	var list = TestObjectsAsRecyclableLongList;
+		// 	var dataCount = TestObjectCountForSlowMethods;
+		// 	for (var i = 0; i < dataCount; i++)
+		// 	{
+		// 		DoNothing(list.Exists((x) => x == data[i]));
+		// 		DoNothing(list.Exists((x) => x == data[^(i + 1)]));
+		// 	}
+		// }
+	}
+}

Recyclable.Collections.Benchmarks/Benchmarks/FindAll_BestAndWorstCases.cs

@@ -0,0 +1,80 @@
+namespace Recyclable.Collections.Benchmarks
+{
+	public partial class RecyclableCollectionsBenchmarks
+	{
+		public void Array_FindAll_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjects;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(Array.FindAll(list, (item) => item == data[i]));
+				DoNothing(Array.FindAll(list, (item) => item == data[^(i + 1)]));
+			}
+		}
+
+		public void List_FindAll_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.FindAll((item) => item == data[i]));
+				DoNothing(list.FindAll((item) => item == data[^(i + 1)]));
+			}
+		}
+
+		public void PooledList_FindAll_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsPooledList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				var temp = list.FindAll((item) => item == data[i]);
+				DoNothing(temp);
+				temp.Dispose();
+
+				temp = list.FindAll((item) => item == data[^(i + 1)]);
+				DoNothing(temp);
+				temp.Dispose();
+			}
+		}
+
+		public void RecyclableList_FindAll_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsRecyclableList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				var temp = list.FindAll((item) => item == data[i]);
+				DoNothing(temp);
+				temp.Dispose();
+
+				temp = list.FindAll((item) => item == data[^(i + 1)]);
+				DoNothing(temp);
+				temp.Dispose();
+			}
+		}
+
+		// public void RecyclableLongList_FindAll_BestAndWorstCases()
+		// {
+		// 	var data = TestObjects;
+		// 	var list = TestObjectsAsRecyclableLongList;
+		// 	var dataCount = TestObjectCountForSlowMethods;
+		// 	for (var i = 0; i < dataCount; i++)
+		// 	{
+		// 		var temp = list.FindAll((item) => item == data[i]);
+		// 		DoNothing(temp);
+		// 		temp.Dispose();
+
+		// 		temp = list.FindAll((item) => item == data[^(i + 1)]);
+		// 		DoNothing(temp);
+		// 		temp.Dispose();
+		// 	}
+		// }
+	}
+}

Recyclable.Collections.Benchmarks/Benchmarks/FindLastIndex_BestAndWorstCases.cs

@@ -0,0 +1,63 @@
+namespace Recyclable.Collections.Benchmarks
+{
+	public partial class RecyclableCollectionsBenchmarks
+	{
+		public void Array_FindLastIndex_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjects;
+			var dataCount = TestObjectCountForSlowMethods;
+			// Console.WriteLine($"{nameof(TestObjectCount)}={TestObjectCount}");
+			// Console.WriteLine($"{nameof(TestObjectCountForSlowMethods)}={TestObjectCountForSlowMethods}");
+			for (var i = 0; i < dataCount; i++)
+			{
+				// Console.WriteLine($"data.Length={data.Length}");
+				// Console.WriteLine($"{nameof(TestObjectCount)}={TestObjectCount}");
+				// Console.WriteLine($"{nameof(TestObjectCountForSlowMethods)}={TestObjectCountForSlowMethods}");
+				DoNothing(Array.FindLastIndex(list, 0, (x) => x == data[i]));
+				DoNothing(Array.FindLastIndex(list, 0, (x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void List_FindLastIndex_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsList;
+			var dataCount = TestObjectCountForSlowMethods;
+			// Console.WriteLine($"{nameof(TestObjectCount)}={TestObjectCount}");
+			// Console.WriteLine($"{nameof(TestObjectCountForSlowMethods)}={TestObjectCountForSlowMethods}");
+			for (var i = 0; i < dataCount; i++)
+			{
+				// Console.WriteLine($"data.Length={data.Length}");
+				// Console.WriteLine($"{nameof(TestObjectCount)}={TestObjectCount}");
+				// Console.WriteLine($"{nameof(TestObjectCountForSlowMethods)}={TestObjectCountForSlowMethods}");
+				DoNothing(list.FindLastIndex(0, (x) => x == data[i]));
+				DoNothing(list.FindLastIndex(0, (x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void RecyclableList_FindLastIndex_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsRecyclableList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.FindLastIndex(0, (x) => x == data[i]));
+				DoNothing(list.FindLastIndex(0, (x) => x == data[^(i + 1)]));
+			}
+		}
+
+		// public void RecyclableLongList_FindLastIndex_BestAndWorstCases()
+		// {
+		// 	var data = TestObjects;
+		// 	var list = TestObjectsAsRecyclableLongList;
+		// 	var dataCount = TestObjectCountForSlowMethods;
+		// 	for (var i = 0; i < dataCount; i++)
+		// 	{
+		// 		DoNothing(list.FindLastIndex(0, (x) => x == data[i]));
+		// 		DoNothing(list.FindLastIndex(0, (x) => x == data[^(i + 1)]));
+		// 	}
+		// }
+	}
+}

Recyclable.Collections.Benchmarks/Benchmarks/FindLast_BestAndWorstCases.cs

@@ -0,0 +1,53 @@
+namespace Recyclable.Collections.Benchmarks
+{
+	public partial class RecyclableCollectionsBenchmarks
+	{
+		public void Array_FindLast_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjects;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(Array.FindLast(list, (x) => x == data[i]));
+				DoNothing(Array.FindLast(list, (x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void List_FindLast_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.FindLast((x) => x == data[i]));
+				DoNothing(list.FindLast((x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void RecyclableList_FindLast_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsRecyclableList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.FindLast((x) => x == data[i]));
+				DoNothing(list.FindLast((x) => x == data[^(i + 1)]));
+			}
+		}
+
+		// public void RecyclableLongList_FindLast_BestAndWorstCases()
+		// {
+		// 	var data = TestObjects;
+		// 	var list = TestObjectsAsRecyclableLongList;
+		// 	var dataCount = TestObjectCountForSlowMethods;
+		// 	for (var i = 0; i < dataCount; i++)
+		// 	{
+		// 		DoNothing(list.FindLast((x) => x == data[i]));
+		// 		DoNothing(list.FindLast((x) => x == data[^(i + 1)]));
+		// 	}
+		// }
+	}
+}

Recyclable.Collections.Benchmarks/Benchmarks/Find_BestAndWorstCases.cs

@@ -0,0 +1,53 @@
+namespace Recyclable.Collections.Benchmarks
+{
+	public partial class RecyclableCollectionsBenchmarks
+	{
+		public void Array_Find_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjects;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(Array.Find(list, (x) => x == data[i]));
+				DoNothing(Array.Find(list, (x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void List_Find_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.Find((x) => x == data[i]));
+				DoNothing(list.Find((x) => x == data[^(i + 1)]));
+			}
+		}
+
+		public void RecyclableList_Find_BestAndWorstCases()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsRecyclableList;
+			var dataCount = TestObjectCountForSlowMethods;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.Find((x) => x == data[i]));
+				DoNothing(list.Find((x) => x == data[^(i + 1)]));
+			}
+		}
+
+		// public void RecyclableLongList_Find_BestAndWorstCases()
+		// {
+		// 	var data = TestObjects;
+		// 	var list = TestObjectsAsRecyclableLongList;
+		// 	var dataCount = TestObjectCountForSlowMethods;
+		// 	for (var i = 0; i < dataCount; i++)
+		// 	{
+		// 		DoNothing(list.Find((x) => x == data[i]));
+		// 		DoNothing(list.Find((x) => x == data[^(i + 1)]));
+		// 	}
+		// }
+	}
+}

Recyclable.Collections.Benchmarks/Benchmarks/RecyclableCollections.Benchmarks.cs

@@ -6,9 +6,11 @@ namespace Recyclable.Collections.Benchmarks
 	public enum RecyclableCollectionsBenchmarkType
 	{
 		Unknown, Add_WithCapacity, Add, AddRange_WithCapacity, AddRangeWhenSourceIsArray, AddRangeWhenSourceIsIEnumerable,
-		AddRangeWhenSourceIsIList, AddRangeWhenSourceIsList, AddRangeWhenSourceIsSameType, Contains_FirstItems,
+		AddRangeWhenSourceIsIList, AddRangeWhenSourceIsList, AddRangeWhenSourceIsSameType, BinarySearch_BestAndWorstCases, 
-		Contains_LastItems, Count, Create_WithCapacity, Create, ForEach, GetItem, IndexOf_BestAndWorstCases, IndexOf_FirstItems,
+		Contains_FirstItems, Contains_LastItems, ConvertAll, Count, Create_WithCapacity, Create, Exists_BestAndWorstCases,
-		IndexOf_LastItems, LongCount, Remove_FirstItems, Remove_LastItems, RemoveAt_FirstItems, RemoveAt_LastItems,
+		Find_BestAndWorstCases, FindAll_BestAndWorstCases, FindLast_BestAndWorstCases, FindLastIndex_BestAndWorstCases,
+		ForEach, GetItem, IndexOf_BestAndWorstCases,IndexOf_FirstItems, IndexOf_LastItems, LongCount,
+		Remove_FirstItems, Remove_LastItems, RemoveAt_FirstItems, RemoveAt_LastItems,
 		SetItem, VersionedForEach
 	}
 
@@ -31,11 +33,18 @@ namespace Recyclable.Collections.Benchmarks
 			RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsIList,
 			RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsList,
 			RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsSameType,
+			RecyclableCollectionsBenchmarkType.BinarySearch_BestAndWorstCases,
 			RecyclableCollectionsBenchmarkType.Contains_FirstItems,
 			RecyclableCollectionsBenchmarkType.Contains_LastItems,
+			RecyclableCollectionsBenchmarkType.ConvertAll,
 			RecyclableCollectionsBenchmarkType.Count,
 			RecyclableCollectionsBenchmarkType.Create_WithCapacity,
 			RecyclableCollectionsBenchmarkType.Create,
+			RecyclableCollectionsBenchmarkType.Exists_BestAndWorstCases,
+			RecyclableCollectionsBenchmarkType.Find_BestAndWorstCases,
+			RecyclableCollectionsBenchmarkType.FindAll_BestAndWorstCases,
+			RecyclableCollectionsBenchmarkType.FindLast_BestAndWorstCases,
+			RecyclableCollectionsBenchmarkType.FindLastIndex_BestAndWorstCases,
 			RecyclableCollectionsBenchmarkType.ForEach,
 			RecyclableCollectionsBenchmarkType.GetItem,
 			RecyclableCollectionsBenchmarkType.IndexOf_BestAndWorstCases,

Recyclable.Collections.Benchmarks/POC/PocBenchmarkBase.cs

@@ -60,7 +60,7 @@ namespace Recyclable.Collections.Benchmarks.POC
 		// [Params(RecyclableDefaults.MinItemsCountForParallelization * 3)]
 		// [Params(1_048_576)]
 		public virtual int TestObjectCount { get; set; } = 0; //8_192;//131_072; //1; //33_554_432; //524_288; //131_072;
-		public virtual int TestObjectCountForSlowMethods => (TestObjectCount / 2) + 1;// Math.Min(TestObjectCount, 131_072);
+		public virtual int TestObjectCountForSlowMethods { get; private set; }
 
 		// [Params(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200)]
 		// [Params(10, 20, 50, 100)]
@@ -103,6 +103,8 @@ namespace Recyclable.Collections.Benchmarks.POC
 		{
 			Console.WriteLine($"******* SETTING UP TEST CASE FOR BENCHMARK {{{DataType}}} *******");
 			
+			TestObjectCountForSlowMethods = (TestObjectCount / 2) + 1;
+			
 			BlockSize = TestObjectCount switch
 			{
 				0 => 1,

Recyclable.Collections.Benchmarks/POC/RecyclableLongListPoc.Benchmarks.cs

@@ -5,24 +5,10 @@ using Recyclable.Collections.Benchmarks.Core;
 
 namespace Recyclable.Collections.Benchmarks.POC
 {
-    public enum RecyclableLongListPocBenchmarkType
-	{
-		EnsureCapacity_ByPowOf2,
-		EnsureCapacityV1_ByPowOf2,
-		EnsureCapacityV3_ByPowOf2,
-	}
-
 	[MemoryDiagnoser]
-	public partial class RecyclableLongListPocBenchmarks : PocBenchmarkBase<RecyclableLongListPocBenchmarkType>
+	public partial class RecyclableLongListPocBenchmarks<T> : PocBenchmarkBase<T>
 	{
-		[Params(RecyclableLongListPocBenchmarkType.EnsureCapacity_ByPowOf2)]
+		private long[]? _testArray;
-		public override RecyclableLongListPocBenchmarkType DataType { get => base.DataType; set => base.DataType = value; }
-
-		// [Params(BenchmarkType.Array, BenchmarkType.List, BenchmarkType.RecyclableList, BenchmarkType.RecyclableLongList)]
-		[Params(RecyclableLongListPocBenchmarkType.EnsureCapacityV1_ByPowOf2)]
-		public override RecyclableLongListPocBenchmarkType BaseDataType { get => base.BaseDataType; set => base.BaseDataType = value; }
-
-        private long[]? _testArray;
 		public long[] TestObjects => _testArray ?? throw new NullReferenceException("Something is wrong and test objects are null");
 
 		public RecyclableLongList<long> TestObjectsAsRecyclableLongList => _testRecyclableLongList ?? throw new NullReferenceException($"Something is wrong and {nameof(RecyclableLongList<long>)} is null");
@@ -31,34 +17,12 @@ namespace Recyclable.Collections.Benchmarks.POC
 		internal PooledList<long> TestPooledList => _testPooledList ?? throw new NullReferenceException($"Something is wrong and {nameof(PooledList<long>)} is null");
 
 		private static readonly MethodInfo _ensureCapacityNewFunc;
-		private static readonly MethodInfo _ensureCapacityV1Func;
-		private static readonly MethodInfo _ensureCapacityV3Func;
 
 		static RecyclableLongListPocBenchmarks()
 		{
 			_ensureCapacityNewFunc = typeof(RecyclableLongList<long>).GetMethod("EnsureCapacity", BindingFlags.Static | BindingFlags.NonPublic)
 				?? throw new NullReferenceException($"Method EnsureCapacity not found in class {nameof(RecyclableLongList<long>)}");
 
-			_ensureCapacityV1Func = typeof(RecyclableLongListV1<long>).GetMethod("EnsureCapacity", BindingFlags.Instance | BindingFlags.NonPublic)
-				?? throw new NullReferenceException($"Method EnsureCapacity not found in class {nameof(RecyclableLongListV1<long>)}");
-
-			_ensureCapacityV3Func = typeof(RecyclableLongListV3<long>).GetMethod("EnsureCapacity", BindingFlags.Static | BindingFlags.NonPublic)
-				?? throw new NullReferenceException($"Method EnsureCapacity not found in class {nameof(RecyclableLongListV3<long>)}");
-		}
-
-		public static void Run()
-		{
-			var benchmark = new RecyclableLongListPocBenchmarks();
-			benchmark.Setup();
-			// benchmark.RecyclableLongList_EnsureCapacity_ByPowOf2();
-			// benchmark.RecyclableLongList_EnsureCapacityV1_ByPowOf2();
-			// benchmark.RecyclableLongList_EnsureCapacityV2_ByPowOf2();
-			// benchmark.RecyclableLongList_EnsureCapacityV3_ByPowOf2();
-			// benchmark.RecyclableLongList_EnsureCapacity_ByBlockSize();
-			// benchmark.RecyclableLongList_EnsureCapacityV1_ByBlockSize();
-			// benchmark.RecyclableLongList_EnsureCapacityV2_ByBlockSize();
-			// benchmark.RecyclableLongList_EnsureCapacityV3_ByBlockSize();
-			benchmark.Cleanup();
 		}
 
 		public override void Setup()
@@ -67,7 +31,7 @@ namespace Recyclable.Collections.Benchmarks.POC
 			_testArray = DataGenerator.EnumerateTestObjects(TestObjectCount);
 
 			base.Setup();
-        }
+		}
 
 		public override void Cleanup()
 		{
@@ -79,18 +43,5 @@ namespace Recyclable.Collections.Benchmarks.POC
 
 			base.Cleanup();
 		}
-
+	}
-        protected override Action? GetTestMethod(RecyclableLongListPocBenchmarkType benchmarkType) => benchmarkType switch
-            {
-                RecyclableLongListPocBenchmarkType.EnsureCapacity_ByPowOf2 => () => RecyclableLongList_EnsureCapacity_ByPowOf2(),
-                RecyclableLongListPocBenchmarkType.EnsureCapacityV1_ByPowOf2 => () => RecyclableLongList_EnsureCapacityV1_ByPowOf2(),
-                RecyclableLongListPocBenchmarkType.EnsureCapacityV3_ByPowOf2 => () => RecyclableLongList_EnsureCapacityV3_ByPowOf2(),
-                _ => throw CreateUnknownBenchmarkTypeException(benchmarkType),
-            };
-
-        protected override void PrepareData<T>(T benchmarkType)
-        {
-			base.PrepareData(benchmarkType);
-        }
-    }
 }

Recyclable.Collections/CompareResult.cs

@@ -0,0 +1,9 @@
+namespace Recyclable.Collections
+{
+	public static class CompareResult
+	{
+		public const int XLessThanY = -1;
+		public const int XEqualY = 0;
+		public const int XGreaterThenY = 1;
+	}
+}

Recyclable.Collections/ComparisonToComparerAdapter.cs

@@ -0,0 +1,32 @@
+namespace Recyclable.Collections
+{
+	public readonly struct ComparisonToComparerAdapter<T> : IComparer<T>
+	{
+		private readonly Comparison<T> _comparison;
+
+		public ComparisonToComparerAdapter(Comparison<T> comparison)
+		{
+			_comparison = comparison;
+		}
+
+		public int Compare(T? x, T? y)
+		{
+			if (x == null && y == null)
+			{
+				return CompareResult.XEqualY;
+			}
+			else if (x != null && y == null)
+			{
+				return CompareResult.XGreaterThenY;
+			}
+			else if (y != null && x == null)
+			{
+				return CompareResult.XLessThanY;
+			}
+			else
+			{
+				return _comparison(x!, y!);
+			}
+		}
+	}
+}

Recyclable.Collections/Pools/RecyclableArrayPool.cs

@@ -7,7 +7,12 @@ namespace Recyclable.Collections.Pools
 		internal static readonly OneSizeArrayPool<T>[] _pools = new OneSizeArrayPool<T>[32];
 		public static T[] RentShared(int blockSize) => _pools[31 - BitOperations.LeadingZeroCount((uint)blockSize)].Rent();
 		public static void ReturnShared(in T[] memoryBlock, bool needsClearing)
-			=> _pools[31 - BitOperations.LeadingZeroCount((uint)memoryBlock.Length)].ReturnUnchecked(memoryBlock, needsClearing);
+		{
+			if (BitOperations.IsPow2(memoryBlock.Length))
+			{
+				_pools[31 - BitOperations.LeadingZeroCount((uint)memoryBlock.Length)].ReturnUnchecked(memoryBlock, needsClearing);
+			}
+		}
 
 		public static ref OneSizeArrayPool<T> Shared(int blockSize)
 			=> ref _pools[31 - BitOperations.LeadingZeroCount((uint)blockSize)];

Recyclable.Collections/RecyclableList.AddRange.cs

@@ -1,48 +1,44 @@
-using System;
 using System.Collections;
-using System.Collections.Generic;
-using System.Linq;
 using System.Numerics;
 using System.Runtime.CompilerServices;
-using System.Threading.Tasks;
 
 namespace Recyclable.Collections
 {
-    public static class zRecyclableListAddRange
+	public static class zRecyclableListAddRange
     {
 		private static void AddRangeEnumerated<T>(this RecyclableList<T> list, IEnumerable<T> items, int growByCount)
 		{
-			int targetItemIndex = list._count;
-			Span<T> memorySpan;
-
-			int i;
 			var enumerator = items.GetEnumerator();
-
+			if (!enumerator.MoveNext())
-			int capacity = list._capacity;
-			memorySpan = new(list._memoryBlock);
-			if (enumerator.MoveNext())
 			{
-				int available = capacity - targetItemIndex;
+				return;
-				do
+			}
-				{
-					if (targetItemIndex + growByCount > capacity)
-					{
-						capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, targetItemIndex, checked((int)BitOperations.RoundUpToPowerOf2((uint)(targetItemIndex + growByCount))));
-						memorySpan = new(list._memoryBlock);
-						available = capacity - targetItemIndex;
-					}
 
-					for (i = 0; i < available; i++)
+			int capacity = list._capacity,
+				targetItemIndex = list._count,
+				available = capacity - targetItemIndex,
+				i;
+
+			Span<T> memorySpan = new(list._memoryBlock);
+			do
+			{
+				if (targetItemIndex + growByCount > capacity)
+				{
+					capacity = RecyclableListHelpers<T>.EnsureCapacity(list, targetItemIndex, checked((int)BitOperations.RoundUpToPowerOf2((uint)(targetItemIndex + growByCount))));
+					memorySpan = new(list._memoryBlock);
+					available = capacity - targetItemIndex;
+				}
+
+				for (i = 0; i < available; i++)
+				{
+					memorySpan[targetItemIndex++] = enumerator.Current;
+					if (!enumerator.MoveNext())
 					{
-						memorySpan[targetItemIndex++] = enumerator.Current;
+						break;
-						if (!enumerator.MoveNext())
-						{
-							break;
-						}
 					}
 				}
-				while (i >= available);
 			}
+			while (i >= available);
 
 			list._capacity = capacity;
 			list._count = targetItemIndex;
@@ -50,7 +46,7 @@ namespace Recyclable.Collections
 
 		private static void AddRangeWithKnownCount<T>(this RecyclableList<T> list, IEnumerable<T> items, int currentItemsCount, int requiredAdditionalCapacity)
 		{
-			list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, currentItemsCount, checked((int)BitOperations.RoundUpToPowerOf2((uint)(currentItemsCount + requiredAdditionalCapacity))));
+			list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, currentItemsCount, checked((int)BitOperations.RoundUpToPowerOf2((uint)(currentItemsCount + requiredAdditionalCapacity))));
 
 			Span<T> memorySpan = new(list._memoryBlock);
 			foreach (var item in items)
@@ -66,10 +62,10 @@ namespace Recyclable.Collections
 		{
 			if (list._capacity < list._count + items.Length)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
 			}
 
-			Array.Copy(items, items.GetLowerBound(0), list._memoryBlock, list._count, items.LongLength);
+			Array.Copy(items, items.GetLowerBound(0), list._memoryBlock, list._count, items.Length);
 			list._count += items.Length;
 			list._version++;
 		}
@@ -79,7 +75,7 @@ namespace Recyclable.Collections
 		{
 			if (list._capacity < list._count + items.Length)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
 			}
 
 			new Span<T>(items).CopyTo(new Span<T>(list._memoryBlock, list._count, items.Length));
@@ -92,7 +88,7 @@ namespace Recyclable.Collections
 		{
 			if (list._capacity < list._count + items.Length)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
 			}
 
 			items.CopyTo(new Span<T>(list._memoryBlock, list._count, items.Length));
@@ -105,7 +101,7 @@ namespace Recyclable.Collections
 		{
 			if (list._capacity < list._count + items.Length)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
 			}
 
 			items.CopyTo(new Span<T>(list._memoryBlock, list._count, items.Length));
@@ -118,7 +114,7 @@ namespace Recyclable.Collections
 		{
 			if (list._capacity < list._count + items.Count)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
 			}
 
 			items.CopyTo(list._memoryBlock, list._count);
@@ -131,7 +127,7 @@ namespace Recyclable.Collections
 		{
 			if (list._capacity < list._count + items.Count)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
 			}
 
 			items.CopyTo(list._memoryBlock, list._count);
@@ -144,7 +140,7 @@ namespace Recyclable.Collections
 		{
 			if (list._capacity < list._count + items.Count)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
 			}
 
 			items.CopyTo(list._memoryBlock, list._count);
@@ -157,7 +153,7 @@ namespace Recyclable.Collections
 		{
 			if (list._capacity < list._count + items._count)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items._count))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items._count))));
 			}
 
 			new Span<T>(items._memoryBlock, 0, items._count).CopyTo(new Span<T>(list._memoryBlock, list._count, items._count));
@@ -183,7 +179,7 @@ namespace Recyclable.Collections
 			int targetCapacity = oldCount + (int)sourceItemsCount;
 			if (list._capacity < targetCapacity)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, oldCount, checked((int)BitOperations.RoundUpToPowerOf2((uint)targetCapacity)));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, oldCount, checked((int)BitOperations.RoundUpToPowerOf2((uint)targetCapacity)));
 			}
 
 			// TODO: Avoid unnecessary range operator - pass as arguments instead.
@@ -233,7 +229,7 @@ namespace Recyclable.Collections
 				{
 					if (targetItemIndex + growByCount > capacity)
 					{
-						capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, targetItemIndex, checked((int)BitOperations.RoundUpToPowerOf2((uint)(targetItemIndex + growByCount))));
+						capacity = RecyclableListHelpers<T>.EnsureCapacity(list, targetItemIndex, checked((int)BitOperations.RoundUpToPowerOf2((uint)(targetItemIndex + growByCount))));
 						memorySpan = new(list._memoryBlock);
 						available = capacity - targetItemIndex;
 					}
@@ -260,7 +256,7 @@ namespace Recyclable.Collections
 			int sourceItemsCount = items.Count;
 			if (list._capacity < list._count + sourceItemsCount)
 			{
-				list._capacity = RecyclableListHelpers<T>.ResizeAndCopy(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + sourceItemsCount))));
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + sourceItemsCount))));
 			}
 
 			Span<T> memorySpan = new(list._memoryBlock, list._count, sourceItemsCount);

Recyclable.Collections/RecyclableList.Compatibility.List.Find.cs

@@ -0,0 +1,271 @@
+using System.Numerics;
+
+namespace Recyclable.Collections
+{
+	public static class zRecyclableListCompatibilityListFind
+	{
+		public static bool Exists<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0)
+			{
+				return false;
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = 0; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return true;
+				}
+			}
+
+			return false;
+		}
+
+		public static T? Find<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0)
+			{
+				return default;
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = 0; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return sourceSpan[itemIndex];
+				}
+			}
+
+			return default;
+		}
+
+		public static RecyclableList<T> FindAll<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0)
+			{
+				return new();
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			RecyclableList<T> result = new(sourceItemsCount >> 3);
+			Span<T> resultSpan = result._memoryBlock;
+			int capacity = result._capacity,
+				resultItemsCount = 0;
+
+			for (var itemIndex = 0; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					if (resultItemsCount + 1 > capacity)
+					{
+						capacity = checked((int)BitOperations.RoundUpToPowerOf2((uint)resultItemsCount + 1));
+						_ = RecyclableListHelpers<T>.EnsureCapacity(result, resultItemsCount, capacity);
+						resultSpan = result._memoryBlock;
+					}
+
+					resultSpan[resultItemsCount++] = sourceSpan[itemIndex];
+				}
+			}
+
+			result._capacity = capacity;
+			result._count = resultItemsCount;
+			return result;
+		}
+		public static RecyclableList<int> FindAllIndexes<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0)
+			{
+				return new();
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			RecyclableList<int> result = new(sourceItemsCount >> 3);
+			Span<int> resultSpan = result._memoryBlock;
+			int capacity = result._capacity,
+				resultItemsCount = 0;
+
+			for (var itemIndex = 0; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					if (resultItemsCount + 1 > capacity)
+					{
+						capacity = checked((int)BitOperations.RoundUpToPowerOf2((uint)resultItemsCount + 1));
+						_ = RecyclableListHelpers<int>.EnsureCapacity(result, resultItemsCount, capacity);
+						resultSpan = result._memoryBlock;
+					}
+
+					resultSpan[resultItemsCount++] = itemIndex;
+				}
+			}
+
+			result._capacity = capacity;
+			result._count = resultItemsCount;
+			return result;
+		}
+
+		public static int FindIndex<T>(this RecyclableList<T> list, int startIndex, int count, Predicate<T> match)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0 || startIndex >= sourceItemsCount)
+			{
+				return RecyclableDefaults.ItemNotFoundIndex;
+			}
+
+			sourceItemsCount = Math.Min(sourceItemsCount, startIndex + sourceItemsCount);
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = startIndex; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return itemIndex;
+				}
+			}
+
+			return RecyclableDefaults.ItemNotFoundIndex;
+		}
+
+		public static int FindIndex<T>(this RecyclableList<T> list, int startIndex, Predicate<T> match)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0 || startIndex >= sourceItemsCount)
+			{
+				return RecyclableDefaults.ItemNotFoundIndex;
+			}
+
+			sourceItemsCount = Math.Min(sourceItemsCount, startIndex + sourceItemsCount);
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = startIndex; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return itemIndex;
+				}
+			}
+
+			return RecyclableDefaults.ItemNotFoundIndex;
+		}
+		
+		public static int FindIndex<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0)
+			{
+				return RecyclableDefaults.ItemNotFoundIndex;
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = 0; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return itemIndex;
+				}
+			}
+
+			return RecyclableDefaults.ItemNotFoundIndex;
+		}
+
+		public static T? FindLast<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			if (list._count == 0)
+			{
+				return default;
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = list._count - 1; itemIndex >= 0; itemIndex--)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return sourceSpan[itemIndex];
+				}
+			}
+
+			return default;
+		}
+
+		public static int FindLastIndex<T>(this RecyclableList<T> list, int startIndex, int count, Predicate<T> match)
+		{
+			if (count == 0)
+			{
+				if (startIndex != -1)
+				{
+					ThrowHelper.ThrowArgumentOutOfRangeException_Index();
+				}
+			}
+			else  if (count < 0 || startIndex - count + 1 < 0)
+			{
+				ThrowHelper.ThrowArgumentOutOfRangeException_Count();
+			}
+
+			if (startIndex < 0)
+			{
+				return RecyclableDefaults.ItemNotFoundIndex;
+			}
+
+			int sourceItemsCount = count; // startIndex - count + 1 >= 0 ? count : startIndex + 1;
+			if (sourceItemsCount == 0)
+			{
+				return RecyclableDefaults.ItemNotFoundIndex;
+			}
+
+			int lastItemIndex = startIndex - sourceItemsCount;
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = startIndex; itemIndex > lastItemIndex; itemIndex--)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return itemIndex;
+				}
+			}
+
+			return RecyclableDefaults.ItemNotFoundIndex;
+		}
+
+		public static int FindLastIndex<T>(this RecyclableList<T> list, int startIndex, Predicate<T> match)
+		{
+			if (list._count == 0 || startIndex < 0)
+			{
+				return RecyclableDefaults.ItemNotFoundIndex;
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = startIndex; itemIndex >= 0; itemIndex--)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return itemIndex;
+				}
+			}
+
+			return RecyclableDefaults.ItemNotFoundIndex;
+		}
+
+		public static int FindLastIndex<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			if (list._count == 0)
+			{
+				return RecyclableDefaults.ItemNotFoundIndex;
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = list._count - 1; itemIndex >= 0; itemIndex--)
+			{
+				if (match(sourceSpan[itemIndex]))
+				{
+					return itemIndex;
+				}
+			}
+
+			return RecyclableDefaults.ItemNotFoundIndex;
+		}
+	}
+}

Recyclable.Collections/RecyclableList.Compatibility.List.IndexOf.cs

@@ -0,0 +1,25 @@
+namespace Recyclable.Collections
+{
+	public static class zRecyclableListCompatibilityListIndexOf
+	{
+		public static int IndexOf<T>(this RecyclableList<T> list, T item, int index) => list._count != 0
+				? Array.IndexOf(list._memoryBlock, item, index, list._count - index)
+				: RecyclableDefaults.ItemNotFoundIndex;
+
+		public static int IndexOf<T>(this RecyclableList<T> list, T item, int index, int count) => list._count != 0
+				? Array.IndexOf(list._memoryBlock, item, index, count)
+				: RecyclableDefaults.ItemNotFoundIndex;
+
+		public static int LastIndexOf<T>(this RecyclableList<T> list, T item) => list._count != 0
+				? Array.LastIndexOf(list._memoryBlock, item, list._count - 1)
+				: RecyclableDefaults.ItemNotFoundIndex;
+
+		public static int LastIndexOf<T>(this RecyclableList<T> list, T item, int index) => list._count != 0
+				? Array.LastIndexOf(list._memoryBlock, item, index)
+				: RecyclableDefaults.ItemNotFoundIndex;
+
+		public static int LastIndexOf<T>(this RecyclableList<T> list, T item, int index, int count) => list._count != 0
+				? Array.LastIndexOf(list._memoryBlock, item, index, count)
+				: RecyclableDefaults.ItemNotFoundIndex;
+	}
+}

Recyclable.Collections/RecyclableList.Compatibility.List.InsertRange.cs

@@ -0,0 +1,357 @@
+using System.Collections;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+
+namespace Recyclable.Collections
+{
+	public static class zRecyclableListCompatibilityListInsertRange
+	{
+		private static void InsertRangeEnumerated<T>(this RecyclableList<T> list, int index, IEnumerable<T> items, int growByCount)
+		{
+			var enumerator = items.GetEnumerator();
+			if (!enumerator.MoveNext())
+			{
+				return;
+			}
+
+			int capacity = list._capacity,
+				added = 0,
+				available = capacity - list._count,
+				i,
+				movingBlockLength = list._count - index;
+
+			T[] memoryBlock = list._memoryBlock;
+			if (available > 0)
+			{
+				Array.Copy(memoryBlock, index, memoryBlock, capacity - movingBlockLength, movingBlockLength);
+			}
+
+			Span<T> memorySpan = new(memoryBlock);
+			do
+			{
+				if (index + available + movingBlockLength > capacity)
+				{
+					var capacityBeforeIncrease = capacity;
+					capacity = checked((int)BitOperations.RoundUpToPowerOf2((uint)(capacity + growByCount)));
+					_ = RecyclableListHelpers<T>.EnsureCapacity(list, memoryBlock.Length, capacity);
+					memorySpan = new(memoryBlock = list._memoryBlock);
+					available = capacity - index - movingBlockLength;
+					Array.Copy(memoryBlock, capacityBeforeIncrease - movingBlockLength, memoryBlock, capacity - movingBlockLength, movingBlockLength);
+				}
+
+				for (i = 0; i < available; i++)
+				{
+					memorySpan[index++] = enumerator.Current;
+					if (!enumerator.MoveNext())
+					{
+						added++;
+						break;
+					}
+				}
+
+				added += i;
+			}
+			while (i == available);
+
+			if (i != available)
+			{
+				Array.Copy(memoryBlock, capacity - movingBlockLength, memoryBlock, index, movingBlockLength);
+				if (RecyclableList<T>._needsClearing)
+				{
+					Array.Clear(memoryBlock, capacity - movingBlockLength, movingBlockLength);
+				}
+			}
+
+			list._count += added;
+			list._capacity = capacity;
+		}
+
+		private static void InsertRangeWithKnownCount<T>(this RecyclableList<T> list, int index, IEnumerable<T> items, int currentItemsCount, int requiredAdditionalCapacity)
+		{
+			list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, currentItemsCount, checked((int)BitOperations.RoundUpToPowerOf2((uint)(currentItemsCount + requiredAdditionalCapacity))));
+
+			Array.Copy(list._memoryBlock, index, list._memoryBlock, index + requiredAdditionalCapacity, list._count - index);
+			Span<T> memorySpan = new(list._memoryBlock);
+			foreach (var item in items)
+			{
+				memorySpan[index++] = item;
+			}
+
+			list._count += requiredAdditionalCapacity;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, in Array items)
+		{
+			if (list._capacity < list._count + items.Length)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Length, list._count - index);
+			Array.Copy(items, items.GetLowerBound(0), memoryBlock, index, items.Length);
+			list._count += items.Length;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, in T[] items)
+		{
+			if (list._capacity < list._count + items.Length)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Length, list._count - index);
+			new Span<T>(items).CopyTo(new Span<T>(memoryBlock, index, items.Length));
+			list._count += items.Length;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, ReadOnlySpan<T> items)
+		{
+			if (list._capacity < list._count + items.Length)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Length, list._count - index);
+			items.CopyTo(new Span<T>(memoryBlock, index, items.Length));
+			list._count += items.Length;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, Span<T> items)
+		{
+			if (list._capacity < list._count + items.Length)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Length))));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Length, list._count - index);
+			items.CopyTo(new Span<T>(memoryBlock, index, items.Length));
+			list._count += items.Length;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, List<T> items)
+		{
+			if (list._capacity < list._count + items.Count)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Count, list._count - index);
+			items.CopyTo(memoryBlock, index);
+			list._count += items.Count;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, ICollection items)
+		{
+			if (list._capacity < list._count + items.Count)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Count, list._count - index);
+			items.CopyTo(list._memoryBlock, index);
+			list._count += items.Count;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, ICollection<T> items)
+		{
+			if (list._capacity < list._count + items.Count)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items.Count))));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Count, list._count - index);
+			items.CopyTo(memoryBlock, index);
+			list._count += items.Count;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, RecyclableList<T> items)
+		{
+			if (list._capacity < list._count + items._count)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + items._count))));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Count, list._count - index);
+			new Span<T>(items._memoryBlock, 0, items._count).CopyTo(new(list._memoryBlock, index, items._count));
+			list._count += items._count;
+			list._version++;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, RecyclableLongList<T> items)
+		{
+			if (items._longCount == 0)
+			{
+				return;
+			}
+
+			int oldCount = list._count;
+			long sourceItemsCount = items._longCount;
+			if (oldCount + sourceItemsCount > int.MaxValue)
+			{
+				ThrowHelper.ThrowArgumentOutOfRangeException(nameof(items), $"The total number of items in source and target table exceeds the maximum capacity of {nameof(RecyclableList<T>)}, equal {int.MaxValue}. Please consider using {nameof(RecyclableLongList<T>)}, instead");
+			}
+
+			int targetCapacity = oldCount + (int)sourceItemsCount;
+			if (list._capacity < targetCapacity)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, oldCount, checked((int)BitOperations.RoundUpToPowerOf2((uint)targetCapacity)));
+			}
+
+			T[] memoryBlock = list._memoryBlock;
+			Array.Copy(memoryBlock, index, memoryBlock, index + items.Count, oldCount - index);
+			Span<T> targetSpan = new(list._memoryBlock, index, list._capacity - index),
+				itemsSpan;
+
+			int blockIndex,
+				sourceBlockSize = items._blockSize,
+				lastBlockIndex = (int)(sourceItemsCount >> items._blockSizePow2BitShift) - 1;
+
+			for (blockIndex = 0; blockIndex <= lastBlockIndex; blockIndex++)
+			{
+				itemsSpan = new(items._memoryBlocks[blockIndex], 0, sourceBlockSize);
+				itemsSpan.CopyTo(targetSpan);
+				targetSpan = targetSpan[sourceBlockSize..];
+			}
+
+			if (blockIndex == 0)
+			{
+				itemsSpan = new(items._memoryBlocks[blockIndex], 0, (int)sourceItemsCount);
+				itemsSpan.CopyTo(targetSpan);
+			}
+			else if (blockIndex <= items._lastBlockWithData)
+			{
+				itemsSpan = new(items._memoryBlocks[blockIndex], 0, items._nextItemIndex > 0 ? items._nextItemIndex : sourceBlockSize);
+				itemsSpan.CopyTo(targetSpan);
+			}
+
+			list._count = targetCapacity;
+			list._version++;
+		}
+
+		public static IEnumerator InsertRange<T>(this RecyclableList<T> list, int index, IEnumerable source, int growByCount = RecyclableDefaults.MinPooledArrayLength)
+		{
+			int targetItemIndex = list._count;
+			Span<T> memorySpan;
+
+			int i;
+			var enumerator = source.GetEnumerator();
+
+			int capacity = list._capacity;
+			memorySpan = new(list._memoryBlock);
+			if (enumerator.MoveNext())
+			{
+				int available = capacity - targetItemIndex;
+				do
+				{
+					if (targetItemIndex + growByCount > capacity)
+					{
+						capacity = RecyclableListHelpers<T>.EnsureCapacity(list, targetItemIndex, checked((int)BitOperations.RoundUpToPowerOf2((uint)(targetItemIndex + growByCount))));
+						memorySpan = new(list._memoryBlock);
+						available = capacity - targetItemIndex;
+					}
+
+					for (i = 0; i < available; i++)
+					{
+						memorySpan[targetItemIndex++] = (T)enumerator.Current;
+						if (!enumerator.MoveNext())
+						{
+							break;
+						}
+					}
+				}
+				while (i >= available);
+			}
+
+			list._capacity = capacity;
+			list._count = targetItemIndex;
+			return enumerator;
+		}
+
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, IReadOnlyList<T> items)
+		{
+			int sourceItemsCount = items.Count;
+			if (list._capacity < list._count + sourceItemsCount)
+			{
+				list._capacity = RecyclableListHelpers<T>.EnsureCapacity(list, list._count, checked((int)BitOperations.RoundUpToPowerOf2((uint)(list._count + sourceItemsCount))));
+			}
+
+			Span<T> memorySpan = new(list._memoryBlock, list._count, sourceItemsCount);
+			for (var sourceItemIndex = 0; sourceItemIndex < sourceItemsCount; sourceItemIndex++)
+			{
+				memorySpan[sourceItemIndex] = items[sourceItemIndex];
+			}
+
+			list._count += sourceItemsCount;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static void InsertRange<T>(this RecyclableList<T> list, int index, IEnumerable<T> items, int growByCount = RecyclableDefaults.MinPooledArrayLength)
+		{
+			if (items is RecyclableList<T> sourceRecyclableList)
+			{
+				InsertRange(list, index, sourceRecyclableList);
+			}
+			else if (items is RecyclableLongList<T> sourceRecyclableLongList)
+			{
+				InsertRange(list, index, sourceRecyclableLongList);
+			}
+			else if (items is T[] sourceArray)
+			{
+				InsertRange(list, index, sourceArray);
+			}
+			else if (items is Array sourceArrayWithObjects)
+			{
+				InsertRange(list, index, sourceArrayWithObjects);
+			}
+			else if (items is List<T> sourceList)
+			{
+				InsertRange(list, index, sourceList);
+			}
+			else if (items is ICollection<T> sourceICollection)
+			{
+				InsertRange(list, index, sourceICollection);
+			}
+			else if (items is ICollection sourceICollectionWithObjects)
+			{
+				InsertRange(list, index, sourceICollectionWithObjects);
+			}
+			else if (items is IReadOnlyList<T> sourceIReadOnlyList)
+			{
+				InsertRange(list, index, sourceIReadOnlyList);
+			}
+			else if (items.TryGetNonEnumeratedCount(out var requiredAdditionalCapacity) && requiredAdditionalCapacity != 0)
+			{
+				InsertRangeWithKnownCount(list, index, items, list._count, requiredAdditionalCapacity);
+			}
+			else
+			{
+				InsertRangeEnumerated(list, index, items, growByCount);
+			}
+		}
+	}
+}

Recyclable.Collections/RecyclableList.Compatibility.List.cs

@@ -0,0 +1,213 @@
+using System.Collections.ObjectModel;
+using System.Numerics;
+using Recyclable.Collections.Pools;
+
+namespace Recyclable.Collections
+{
+
+	public static class zRecyclableListCompatibilityList
+	{
+		public static ReadOnlyCollection<T> AsReadOnly<T>(this RecyclableList<T> list) => new(list);
+
+		public static int BinarySearch<T>(this RecyclableList<T> list, T item)
+			=> Array.BinarySearch(list._memoryBlock, 0, list._count, item);
+
+		public static int BinarySearch<T>(this RecyclableList<T> list, T item, IComparer<T>? comparer)
+			=> Array.BinarySearch(list._memoryBlock, 0, list._count, item, comparer);
+
+		public static int BinarySearch<T>(this RecyclableList<T> list, int index, int count, T item, IComparer<T>? comparer)
+			=> Array.BinarySearch(list._memoryBlock, index, count, item, comparer);
+
+		public static RecyclableList<TOutput> ConvertAll<T, TOutput>(this RecyclableList<T> list, Converter<T, TOutput> converter)
+		{
+			int itemsCount = list._count;
+			if (itemsCount == 0)
+			{
+				return new();
+			}
+
+			RecyclableList<TOutput> result = new(itemsCount);
+			TOutput[] resultSpan = result._memoryBlock;			
+			ReadOnlySpan<T> sourceSpan = list._memoryBlock;
+			for (int bufferIndex = 0; bufferIndex < itemsCount; bufferIndex++)
+			{
+				resultSpan[bufferIndex] = converter(sourceSpan[bufferIndex]);
+			}
+
+			result._count = itemsCount;
+			return result;
+		}
+
+		public static void CopyTo<T>(this RecyclableList<T> list, T[] array) => Array.Copy(list._memoryBlock, array, list._count);
+
+		public static void CopyTo<T>(this RecyclableList<T> list, int index, T[] array, int arrayIndex, int count) => Array.Copy(list._memoryBlock, index, array, arrayIndex, count);
+
+		public static void ForEach<T>(this RecyclableList<T> list, Action<T> action)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0)
+			{
+				return;
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = 0; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				action(sourceSpan[itemIndex]);
+			}
+		}
+
+		public static RecyclableList<T> GetRange<T>(this RecyclableList<T> list, int index, int count)
+		{
+			int sourceItemsCount = index + count <= list._count ? count : list._count - index;
+			if (sourceItemsCount <= 0)
+			{
+				return new();
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			RecyclableList<T> result = new(sourceItemsCount);
+			Span<T> resultSpan = result._memoryBlock;
+			int resultItemsCount = 0;
+			sourceItemsCount += index;
+			for (var itemIndex = index; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				resultSpan[resultItemsCount++] = sourceSpan[itemIndex];
+			}
+
+			result._count = resultItemsCount;
+			return result;
+		}
+
+		public static int RemoveAll<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			using var allIndexes = list.FindAllIndexes(match);
+			int foundItemsCount = allIndexes._count;
+			if (foundItemsCount == 0)
+			{
+				return foundItemsCount;
+			}
+
+			for (int removed = 0; removed < foundItemsCount; removed++)
+			{
+				var indexToRemove = allIndexes[removed] - removed;
+				Array.Copy(list._memoryBlock, indexToRemove + 1, list._memoryBlock, indexToRemove, list._count - indexToRemove - removed - 1);
+			}
+
+			if (RecyclableList<T>._needsClearing)
+			{
+				Array.Clear(list._memoryBlock, list._count - foundItemsCount, foundItemsCount);
+			}
+
+			list._count -= foundItemsCount;
+			list._version++;
+			return foundItemsCount;
+		}
+
+		public static void RemoveRange<T>(this RecyclableList<T> list, int index, int count)
+		{
+			int oldCount = list._count;
+			count = count - index + 1 <= oldCount ? count : oldCount - index + 1;
+			if (count == 0)
+			{
+				return;
+			}
+
+			if (index + count < oldCount)
+			{
+				Array.Copy(list._memoryBlock, index + count, list._memoryBlock, index, oldCount - count - index);
+			}
+
+			if (RecyclableList<T>._needsClearing)
+			{
+				Array.Clear(list._memoryBlock, oldCount - count, count);
+			}
+
+			list._count -= count;
+			list._version++;
+		}
+
+		public static void Reverse<T>(this RecyclableList<T> list)
+		{
+			Array.Reverse(list._memoryBlock, 0, list._count);
+			list._version++;
+		}
+
+		public static void Reverse<T>(this RecyclableList<T> list, int index, int count)
+		{
+			Array.Reverse(list._memoryBlock, index, count);
+			list._version++;
+		}
+
+		public static void Sort<T>(this RecyclableList<T> list)
+		{
+			Array.Sort(list._memoryBlock, 0, list._count);
+			list._version++;
+		}
+
+		public static void Sort<T>(this RecyclableList<T> list, Comparison<T> comparison)
+		{
+			Array.Sort(list._memoryBlock, 0, list._count, new ComparisonToComparerAdapter<T>(comparison));
+			list._version++;
+		}
+
+		public static void Sort<T>(this RecyclableList<T> list, IComparer<T>? comparer)
+		{
+			Array.Sort(list._memoryBlock, 0, list._count, comparer);
+			list._version++;
+		}
+
+		public static void Sort<T>(this RecyclableList<T> list, int index, int count, IComparer<T>? comparer)
+		{
+			Array.Sort(list._memoryBlock, index, count, comparer);
+			list._version++;
+		}
+
+		public static T[] ToArray<T>(this RecyclableList<T> list)
+		{
+			T[] result = new T[list._count];
+			new Span<T>(list._memoryBlock, 0, list._count).CopyTo(new Span<T>(result));
+			return result;
+		}
+
+		public static void TrimExcess<T>(this RecyclableList<T> list)
+		{
+			var requiredCapacity = list._count >= RecyclableDefaults.InitialCapacity ? list._count : RecyclableDefaults.InitialCapacity;
+
+			T[] oldMemoryBlock = list._memoryBlock;
+			T[] result = requiredCapacity >= RecyclableDefaults.MinPooledArrayLength && BitOperations.IsPow2(requiredCapacity)
+				? RecyclableArrayPool<T>.RentShared(requiredCapacity)
+				: new T[requiredCapacity];
+
+			new Span<T>(oldMemoryBlock, 0, list._count).CopyTo(new(result));
+
+			if (oldMemoryBlock.Length >= RecyclableDefaults.MinPooledArrayLength)
+			{
+				RecyclableArrayPool<T>.ReturnShared(oldMemoryBlock, RecyclableList<T>._needsClearing);
+			}
+
+			list._memoryBlock = result;
+			list._capacity = requiredCapacity;
+		}
+
+		public static bool TrueForAll<T>(this RecyclableList<T> list, Predicate<T> match)
+		{
+			int sourceItemsCount = list._count;
+			if (sourceItemsCount == 0)
+			{
+				return false;
+			}
+
+			ReadOnlySpan<T> sourceSpan = new(list._memoryBlock);
+			for (var itemIndex = 0; itemIndex < sourceItemsCount; itemIndex++)
+			{
+				if (!match(sourceSpan[itemIndex]))
+				{
+					return false;
+				}
+			}
+
+			return true;
+		}
+	}
+}

Recyclable.Collections/RecyclableList.Helpers.cs

@@ -7,104 +7,10 @@ namespace Recyclable.Collections
 	{
 		private static readonly bool NeedsClearing = !typeof(T).IsValueType;
 
-		[Obsolete("This method MAY be removed in the near future.")]
+		public static int CalculateIndex(int index, int lowerBound) => index >= 0 ? index + lowerBound : RecyclableDefaults.ItemNotFoundIndex;
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public static bool Contains(RecyclableList<T[]> arrays, T item) => arrays.Any(x => x.Contains(item));
-
-		[Obsolete("This method MAY be removed in the near future.")]
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public static void CopyTo(RecyclableList<T[]> arrays, long startingIndex, int blockSize, int lastBlockSize, T[] destinationArray, int destinationArrayIndex)
-		{
-			Span<T> arrayMemory = destinationArray.AsSpan();
-			arrayMemory = arrayMemory[destinationArrayIndex..];
-			// TODO: Convert "/" & "%" to bit-shifting
-			int startingArrayIndex = (int)(startingIndex / blockSize);
-			startingIndex %= blockSize;
-			if (arrays._count > 0)
-			{
-				ReadOnlySpan<T> sourceMemory = arrays[0].AsSpan();
-				var maxToCopy = (int)Math.Min(blockSize - startingIndex, arrayMemory.Length);
-				if (arrays._count == 1)
-				{
-					maxToCopy = Math.Min(maxToCopy, lastBlockSize);
-				}
-
-				sourceMemory = sourceMemory[(int)startingIndex..maxToCopy];
-				sourceMemory.CopyTo(arrayMemory);
-				arrayMemory = arrayMemory[maxToCopy..];
-			}
-
-			for (var arrayIdx = startingArrayIndex + 1; arrayIdx < arrays._count - 1 && arrayMemory.Length > 0; arrayIdx++)
-			{
-				ReadOnlySpan<T> sourceMemory = arrays[arrayIdx].AsSpan();
-				var maxToCopy = Math.Min(blockSize, arrayMemory.Length);
-				sourceMemory = sourceMemory[..maxToCopy];
-				sourceMemory.CopyTo(arrayMemory);
-				arrayMemory = arrayMemory[maxToCopy..];
-			}
-
-			if (arrays._count > 1 && arrayMemory.Length > 0)
-			{
-				ReadOnlySpan<T> sourceMemory = arrays[^1].AsSpan();
-				var maxToCopy = Math.Min(lastBlockSize, arrayMemory.Length);
-				sourceMemory = sourceMemory[..maxToCopy];
-				sourceMemory.CopyTo(arrayMemory);
-			}
-		}
-
-		[Obsolete("This method WILL be removed in the near future. Please use the existing enumerators instead of it.")]
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public static IEnumerable<T> Enumerate(RecyclableList<T[]> arrays, int chunkSize, long totalCount)
-		{
-			long currentCount = 0;
-			for (var arrayIdx = 0; (arrayIdx < arrays._count) && (currentCount < totalCount); arrayIdx++)
-			{
-				var array = arrays[arrayIdx];
-				currentCount += Math.Min(chunkSize, totalCount);
-				switch (currentCount < totalCount)
-				{
-					case true:
-						for (var valueIdx = 0; valueIdx < chunkSize; valueIdx++)
-						{
-							yield return array[valueIdx];
-						}
-
-						break;
-
-					case false:
-						var partialCount = (int)(totalCount % chunkSize);
-						int maxCount = partialCount > 0 ? partialCount : chunkSize;
-						for (var valueIdx = 0; valueIdx < maxCount; valueIdx++)
-						{
-							yield return array[valueIdx];
-						}
-
-						break;
-				}
-			}
-		}
-
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public static long LongIndexOf(RecyclableList<T[]> arrays, int blockSize, T item, IEqualityComparer<T> comparer)
-		{
-			for (var arrayIdx = 0; arrayIdx < arrays._count; arrayIdx++)
-			{
-				var array = arrays[arrayIdx];
-				Span<T> arrayMemory = array.AsSpan();
-				for (int memoryIdx = 0; memoryIdx < arrayMemory.Length; memoryIdx++)
-				{
-					if (comparer.Equals(arrayMemory[memoryIdx], item))
-					{
-						return (arrayIdx * (long)blockSize) + memoryIdx;
-					}
-				}
-			}
-
-			return -1;
-		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
-		public static void ResizeAndCopy(RecyclableList<T> list)
+		public static void EnsureCapacity(RecyclableList<T> list)
 		{
 			// TODO: Measure performance
 			// T[] newMemoryBlock = RecyclableListHelpers<T>._arrayPool.Rent(_capacity <<= 1);
@@ -129,14 +35,38 @@ namespace Recyclable.Collections
 		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
-		public static int ResizeAndCopy(RecyclableList<T> sourceList, int oldSize, int newSize)
+		public static int EnsureCapacity(RecyclableList<T> sourceList, int newSize)
 		{
 			T[] oldMemoryBlock = sourceList._memoryBlock;
 			sourceList._memoryBlock = newSize >= RecyclableDefaults.MinPooledArrayLength
 				? RecyclableArrayPool<T>.RentShared(newSize)
 				: new T[newSize];
 
-			// & WAS SLOWER WITHOUT
+			// & WAS SLOWER AS ARRAY
+			new Span<T>(oldMemoryBlock, 0, sourceList._capacity).CopyTo(sourceList._memoryBlock);
+
+			if (oldMemoryBlock.Length >= RecyclableDefaults.MinPooledArrayLength)
+			{
+				// TODO: Measure gain vs relying on arrayPool to clear
+				//if (NeedsClearing)
+				//{
+				//	Array.Clear(source);
+				//}
+
+				// If anything, it has been already cleared above, so we don't need to repeat it.
+				RecyclableArrayPool<T>.ReturnShared(oldMemoryBlock, NeedsClearing);
+			}
+
+			return newSize;
+		}
+
+		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+		public static int EnsureCapacity(RecyclableList<T> sourceList, int oldSize, int newSize)
+		{
+			T[] oldMemoryBlock = sourceList._memoryBlock;
+			sourceList._memoryBlock = newSize >= RecyclableDefaults.MinPooledArrayLength
+				? RecyclableArrayPool<T>.RentShared(newSize)
+				: new T[newSize];
 
 			// & WAS SLOWER AS ARRAY
 			new Span<T>(oldMemoryBlock, 0, oldSize).CopyTo(sourceList._memoryBlock);

Recyclable.Collections/RecyclableList.cs

@@ -8,7 +8,7 @@ namespace Recyclable.Collections
 	[Serializable]
 	public sealed partial class RecyclableList<T> : IList<T>, IReadOnlyList<T>, IDisposable
 	{
-		private static readonly bool _needsClearing = !typeof(T).IsValueType;
+		internal static readonly bool _needsClearing = !typeof(T).IsValueType;
 
 		public static explicit operator ReadOnlySpan<T>(RecyclableList<T> source) => new(source._memoryBlock, 0, source._count);
 
@@ -41,6 +41,22 @@ namespace Recyclable.Collections
 			}
 		}
 
+		public RecyclableList(int initialCapacity, int lowerBound)
+		{
+			if (initialCapacity >= RecyclableDefaults.InitialCapacity)
+			{
+				_memoryBlock = initialCapacity >= RecyclableDefaults.MinPooledArrayLength
+					? RecyclableArrayPool<T>.RentShared(checked((int)BitOperations.RoundUpToPowerOf2((uint)initialCapacity)))
+					: new T[initialCapacity];
+				_capacity = _memoryBlock.Length;
+			}
+			else
+			{
+				_memoryBlock = new T[RecyclableDefaults.InitialCapacity];
+				_capacity = RecyclableDefaults.InitialCapacity;
+			}
+		}
+
 		public RecyclableList(in Array source)
 		{
 			_capacity = RecyclableDefaults.InitialCapacity;
@@ -168,14 +184,30 @@ namespace Recyclable.Collections
 			{
 				if (_capacity != value)
 				{
-					_capacity = RecyclableListHelpers<T>.ResizeAndCopy(this, _count, checked((int)BitOperations.RoundUpToPowerOf2((uint)value)));
+					_capacity = RecyclableListHelpers<T>.EnsureCapacity(this, _count, checked((int)BitOperations.RoundUpToPowerOf2((uint)value)));
 					_version++;
 				}
 			}
 		}
 
 		internal int _count;
-		public int Count => _count;
+		public int Count
+		{
+			get => _count;
+			set
+			{
+				if (_count != value)
+				{
+					if (value > _capacity)
+					{
+						_capacity = RecyclableListHelpers<T>.EnsureCapacity(this, _capacity, checked((int)BitOperations.RoundUpToPowerOf2((uint)value)));
+					}
+
+					_count = value;
+					_version++;
+				}
+			}
+		}
 
 		public bool IsReadOnly => false;
 
@@ -184,7 +216,14 @@ namespace Recyclable.Collections
 		{
 			if (_count >= _capacity)
 			{
-				RecyclableListHelpers<T>.ResizeAndCopy(this);
+				if (BitOperations.IsPow2(_capacity))
+				{
+					RecyclableListHelpers<T>.EnsureCapacity(this);
+				}
+				else
+				{
+					_capacity = RecyclableListHelpers<T>.EnsureCapacity(this, (int)BitOperations.RoundUpToPowerOf2((uint)_capacity));
+				}
 			}
 
 			_memoryBlock[_count++] = item;
@@ -217,7 +256,9 @@ namespace Recyclable.Collections
 		public void CopyTo(T[] array, int index) => Array.Copy(_memoryBlock, 0, array, index, _count);
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public int IndexOf(T itemToFind) => _count != 0 ? Array.IndexOf(_memoryBlock, itemToFind, 0, _count) : RecyclableDefaults.ItemNotFoundIndex;
+		public int IndexOf(T itemToFind) => _count != 0
+				? Array.IndexOf(_memoryBlock, itemToFind, 0, _count)
+				: RecyclableDefaults.ItemNotFoundIndex;
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
 		public void Insert(int index, T item)
@@ -225,11 +266,13 @@ namespace Recyclable.Collections
 			int oldCount = _count;
 			if (_capacity < oldCount + 1)
 			{
-				_capacity = RecyclableListHelpers<T>.ResizeAndCopy(this, oldCount, checked((int)BitOperations.RoundUpToPowerOf2((uint)oldCount + 1)));
+				_capacity = RecyclableListHelpers<T>.EnsureCapacity(this, oldCount, checked((int)BitOperations.RoundUpToPowerOf2((uint)oldCount + 1)));
 			}
 
 			if (index < oldCount)
 			{
+				// TODO: Compare performance
+				// Array.Copy(_memoryBlock, index, _memoryBlock, index + 1, oldCount);
 				new Span<T>(_memoryBlock, index, oldCount -= index)
 					.CopyTo(new Span<T>(_memoryBlock, index + 1, oldCount));
 			}

Recyclable.Collections/RecyclableQueue.Helpers.cs

@@ -2,12 +2,109 @@ using System.Runtime.CompilerServices;
 
 namespace Recyclable.Collections
 {
-	internal static class RecyclableQueueHelpers
+	internal static class RecyclableQueueHelpers<T>
 	{
+		[Obsolete("This method MAY be removed in the near future.")]
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		internal static bool Contains(RecyclableList<T[]> arrays, T item) => arrays.Any(x => x.Contains(item));
+
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public static int ToArrayIndex(long index, int blockSize) => (int)(index / blockSize);
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public static long ToItemIndex(long index, int blockSize) => index % blockSize;
+
+		[Obsolete("This method MAY be removed in the near future.")]
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		internal static void CopyTo(RecyclableList<T[]> arrays, long startingIndex, int blockSize, int lastBlockSize, T[] destinationArray, int destinationArrayIndex)
+		{
+			Span<T> arrayMemory = destinationArray.AsSpan();
+			arrayMemory = arrayMemory[destinationArrayIndex..];
+			// TODO: Convert "/" & "%" to bit-shifting
+			int startingArrayIndex = (int)(startingIndex / blockSize);
+			startingIndex %= blockSize;
+			if (arrays._count > 0)
+			{
+				ReadOnlySpan<T> sourceMemory = arrays[0].AsSpan();
+				var maxToCopy = (int)Math.Min(blockSize - startingIndex, arrayMemory.Length);
+				if (arrays._count == 1)
+				{
+					maxToCopy = Math.Min(maxToCopy, lastBlockSize);
+				}
+
+				sourceMemory = sourceMemory[(int)startingIndex..maxToCopy];
+				sourceMemory.CopyTo(arrayMemory);
+				arrayMemory = arrayMemory[maxToCopy..];
+			}
+
+			for (var arrayIdx = startingArrayIndex + 1; arrayIdx < arrays._count - 1 && arrayMemory.Length > 0; arrayIdx++)
+			{
+				ReadOnlySpan<T> sourceMemory = arrays[arrayIdx].AsSpan();
+				var maxToCopy = Math.Min(blockSize, arrayMemory.Length);
+				sourceMemory = sourceMemory[..maxToCopy];
+				sourceMemory.CopyTo(arrayMemory);
+				arrayMemory = arrayMemory[maxToCopy..];
+			}
+
+			if (arrays._count > 1 && arrayMemory.Length > 0)
+			{
+				ReadOnlySpan<T> sourceMemory = arrays[^1].AsSpan();
+				var maxToCopy = Math.Min(lastBlockSize, arrayMemory.Length);
+				sourceMemory = sourceMemory[..maxToCopy];
+				sourceMemory.CopyTo(arrayMemory);
+			}
+		}
+
+		[Obsolete("This method WILL be removed in the near future. Please use the existing enumerators instead of it.")]
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		internal static IEnumerable<T> Enumerate(RecyclableList<T[]> arrays, int chunkSize, long totalCount)
+		{
+			long currentCount = 0;
+			for (var arrayIdx = 0; (arrayIdx < arrays._count) && (currentCount < totalCount); arrayIdx++)
+			{
+				var array = arrays[arrayIdx];
+				currentCount += Math.Min(chunkSize, totalCount);
+				switch (currentCount < totalCount)
+				{
+					case true:
+						for (var valueIdx = 0; valueIdx < chunkSize; valueIdx++)
+						{
+							yield return array[valueIdx];
+						}
+
+						break;
+
+					case false:
+						var partialCount = (int)(totalCount % chunkSize);
+						int maxCount = partialCount > 0 ? partialCount : chunkSize;
+						for (var valueIdx = 0; valueIdx < maxCount; valueIdx++)
+						{
+							yield return array[valueIdx];
+						}
+
+						break;
+				}
+			}
+		}
+
+		[Obsolete]
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		internal static long LongIndexOf(RecyclableList<T[]> arrays, int blockSize, T item, IEqualityComparer<T> comparer)
+		{
+			for (var arrayIdx = 0; arrayIdx < arrays._count; arrayIdx++)
+			{
+				var array = arrays[arrayIdx];
+				Span<T> arrayMemory = array.AsSpan();
+				for (int memoryIdx = 0; memoryIdx < arrayMemory.Length; memoryIdx++)
+				{
+					if (comparer.Equals(arrayMemory[memoryIdx], item))
+					{
+						return (arrayIdx * (long)blockSize) + memoryIdx;
+					}
+				}
+			}
+
+			return -1;
+		}
 	}
 }

Recyclable.Collections/RecyclableQueue.cs

@@ -99,8 +99,8 @@ namespace Recyclable.Collections
 		private void SetItem(long index, T value)
 		{
 			long absoluteIndex = GetAbsoluteIndex(index, RemovedCount);
-			int arrayIndex = RecyclableQueueHelpers.ToArrayIndex(absoluteIndex, BlockSize);
+			int arrayIndex = RecyclableQueueHelpers<T>.ToArrayIndex(absoluteIndex, BlockSize);
-			long itemIndex = RecyclableQueueHelpers.ToItemIndex(absoluteIndex, BlockSize);
+			long itemIndex = RecyclableQueueHelpers<T>.ToItemIndex(absoluteIndex, BlockSize);
 			Memory[arrayIndex][itemIndex] = value;
 		}
 
@@ -108,8 +108,8 @@ namespace Recyclable.Collections
 		private T GetItem(long index)
 		{
 			long absoluteIndex = GetAbsoluteIndex(index, RemovedCount);
-			int arrayIndex = RecyclableQueueHelpers.ToArrayIndex(absoluteIndex, BlockSize);
+			int arrayIndex = RecyclableQueueHelpers<T>.ToArrayIndex(absoluteIndex, BlockSize);
-			long itemIndex = RecyclableQueueHelpers.ToItemIndex(absoluteIndex, BlockSize);
+			long itemIndex = RecyclableQueueHelpers<T>.ToItemIndex(absoluteIndex, BlockSize);
 			return Memory[arrayIndex][itemIndex];
 		}
 
@@ -166,13 +166,13 @@ namespace Recyclable.Collections
 		}
 
 #pragma	warning disable CS0618
-		public bool Contains(T item) => RecyclableListHelpers<T>.Contains(Memory, item);
+		public bool Contains(T item) => RecyclableQueueHelpers<T>.Contains(Memory, item);
-		public void CopyTo(T[] array, int arrayIndex) => RecyclableListHelpers<T>.CopyTo(Memory, RemovedCount, BlockSize, (int)(LongCount % BlockSize), array, arrayIndex);
+		public void CopyTo(T[] array, int arrayIndex) => RecyclableQueueHelpers<T>.CopyTo(Memory, RemovedCount, BlockSize, (int)(LongCount % BlockSize), array, arrayIndex);
-		public IEnumerable<T> Enumerate() => RecyclableListHelpers<T>.Enumerate(Memory, BlockSize, LongCount);
+		public IEnumerable<T> Enumerate() => RecyclableQueueHelpers<T>.Enumerate(Memory, BlockSize, LongCount);
-		public IEnumerator<T> GetEnumerator() => RecyclableListHelpers<T>.Enumerate(Memory, BlockSize, LongCount).GetEnumerator();
+		public IEnumerator<T> GetEnumerator() => RecyclableQueueHelpers<T>.Enumerate(Memory, BlockSize, LongCount).GetEnumerator();
-		IEnumerator IEnumerable.GetEnumerator() => RecyclableListHelpers<T>.Enumerate(Memory, BlockSize, LongCount).GetEnumerator();
+		IEnumerator IEnumerable.GetEnumerator() => RecyclableQueueHelpers<T>.Enumerate(Memory, BlockSize, LongCount).GetEnumerator();
-		public int IndexOf(T item) => (int)GetRelativeIndex(RecyclableListHelpers<T>.LongIndexOf(Memory, BlockSize, item, _equalityComparer));
+		public int IndexOf(T item) => (int)GetRelativeIndex(RecyclableQueueHelpers<T>.LongIndexOf(Memory, BlockSize, item, _equalityComparer));
-		public long LongIndexOf(T item) => GetRelativeIndex(RecyclableListHelpers<T>.LongIndexOf(Memory, BlockSize, item, _equalityComparer));
+		public long LongIndexOf(T item) => GetRelativeIndex(RecyclableQueueHelpers<T>.LongIndexOf(Memory, BlockSize, item, _equalityComparer));
 #pragma warning restore CS0618
 
 		public void Insert(int index, T item) => throw new NotSupportedException();

Recyclable.Collections/ThrowHelper.cs

@@ -8,15 +8,9 @@ namespace Recyclable.Collections
 		/// This is a helper method to throw <see cref="ArgumentOutOfRangeException"/> with the given message.
 		/// </summary>
 		/// <exception cref="ArgumentOutOfRangeException">Always</exception>
-		public static void ThrowArgumentOutOfRangeException(string argumentName, string message)
+		public static void ThrowArgumentOutOfRangeException(string argumentName, string message) => throw new ArgumentOutOfRangeException(argumentName, message);
-		{
+		public static void ThrowWrongReturnedArraySizeException(int returnedLength, int blockSize) => throw new InvalidOperationException($"The array size {returnedLength} doesn't match the size {blockSize} of the pool buffer and cannot be returned to this pool.");
-			Contract.EnsuresOnThrow<ArgumentOutOfRangeException>(false);
+		public static void ThrowArgumentOutOfRangeException_Index() => throw new ArgumentOutOfRangeException("index", "Parameter `index` has invalid value. It must be within the no. of elements in the collection");
-			throw new ArgumentOutOfRangeException(argumentName, message);
+		public static void ThrowArgumentOutOfRangeException_Count() => throw new ArgumentOutOfRangeException("index", "Parameter `count` has invalid value. Combined with index, it must be within the no. of elements in the collection");
-		}
-
-		public static void ThrowWrongReturnedArraySizeException(int returnedLength, int blockSize)
-		{
-			throw new InvalidOperationException($"The array size {returnedLength} doesn't match the size {blockSize} of the pool buffer and cannot be returned to this pool.");
-		}
 	}
 }

Recyclable.CollectionsTests/RecyclableLongListTestData.cs

@@ -1,7 +1,6 @@
 using MoreLinq;
 using Open.Numeric.Primes;
 using Recyclable.Collections;
-using System.Collections;
 using System.Numerics;
 
 namespace Recyclable.CollectionsTests
@@ -34,6 +33,8 @@ namespace Recyclable.CollectionsTests
 			0, 1, 2, 3, 7, 10, 16, RecyclableDefaults.MinPooledArrayLength - 5, RecyclableDefaults.MinPooledArrayLength - 1, RecyclableDefaults.MinPooledArrayLength, RecyclableDefaults.MinPooledArrayLength + 1, RecyclableDefaults.MinPooledArrayLength + 5, RecyclableDefaults.MinPooledArrayLength * 100
 		};
 
+		public static readonly IEnumerable<object[]> ItemsCountTestCases = ItemsCountVariants.Select(x => new object[] { (int)x });
+
 		public static readonly IEnumerable<int> BlockSizeVariants = new int[]
 		{
 			1, 2, 4, 16, RecyclableDefaults.MinPooledArrayLength - 5, (int)BitOperations.RoundUpToPowerOf2(RecyclableDefaults.MinPooledArrayLength)