just a first experimental version

git-svn-id: svn://svn.code.sf.net/p/ultrastardx/svn/branches/experimental@2011 b956fd51-792f-4845-bead-9b4dfca2ff2c

1 files changed, 5318 insertions, 0 deletions

diff --git a/Medley/src/lib/collections/Collections.pas b/Medley/src/lib/collections/Collections.pas
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+unit Collections;
+(*****************************************************************************
+ * Copyright 2003 by Matthew Greet
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
+ * details. (http://opensource.org/licenses/lgpl-license.php)
+ * 
+ * See http://www.warmachine.u-net.com/delphi_collections for updates and downloads.
+ *
+ * $Version: v1.0 $
+ * $Revision: 1.1.1.4 $
+ * $Log: D:\QVCS Repositories\Delphi Collections\Collections.qbt $
+ * 
+ *   Main unit containing all interface and abstract class definitions.
+ * 
+ * Revision 1.1.1.4  by: Matthew Greet  Rev date: 14/03/05 23:26:32
+ *   Fixed RemoveAll for TAbstractList for sorted lists.
+ * 
+ * Revision 1.1.1.3  by: Matthew Greet  Rev date: 14/10/04 16:31:18
+ *   Fixed memory lean in ContainsKey of TAbstractStringMap and
+ *   TAbstractIntegerMap.
+ * 
+ * Revision 1.1.1.2  by: Matthew Greet  Rev date: 12/06/04 20:03:26
+ *   Capacity property. 
+ *   Memory leak fixed.
+ * 
+ * Revision 1.1.1.1  by: Matthew Greet  Rev date: 13/02/04 16:12:10
+ *   v1.0 branch.
+ * 
+ * Revision 1.1  by: Matthew Greet  Rev date: 06/04/03 10:36:30
+ *   Added integer map and string map collection types with supporting
+ *   classes. 
+ *   Add clone and filter functions with supporting classes. 
+ *   Added nil not allowed collection error. 
+ *   Properties appear in collection interfaces as well as abstract
+ *   classes.
+ * 
+ * Revision 1.0  by: Matthew Greet  Rev date: 01/03/03 10:50:02
+ *   Initial revision.
+ * 
+ * FPC compatibility fixes by: UltraStar Deluxe Team
+ *
+ * $Endlog$
+ *****************************************************************************)
+
+{$IFDEF FPC}
+  {$MODE Delphi}{$H+}
+{$ENDIF}
+ 
+interface
+
+uses
+    Classes, SysUtils;
+
+const
+    EquatableIID: TGUID = '{EAC823A7-0B90-11D7-8120-0002E3165EF8}';
+    HashableIID: TGUID = '{98998440-4C3E-11D7-8120-0002E3165EF8}';
+    ComparableIID: TGUID = '{9F4C96C0-0CF0-11D7-8120-0002E3165EF8}';
+    MappableIID: TGUID = '{DAEC8CA0-0DBB-11D7-8120-0002E3165EF8}';
+    StringMappableIID: TGUID = '{3CC61F40-5F92-11D7-8120-0002E3165EF8}';
+    IntegerMappableIID: TGUID = '{774FC760-5F92-11D7-8120-0002E3165EF8}';
+
+type
+    TDefaultComparator = class;
+    TNaturalComparator = class;
+    ICollectable = interface;
+
+    TCollectableArray = array of ICollectable;
+    TIntegerArray = array of Integer;
+    TStringArray = array of String;
+    TListArray = array of TList;
+
+    TCollectionError = (ceOK, ceDuplicate, ceDuplicateKey, ceFixedSize, ceNilNotAllowed, ceNotNaturalItem, ceOutOfRange);
+    TCollectionErrors = set of TCollectionError;
+
+    TSearchResultType = (srNotFound, srFoundAtIndex, srBeforeIndex, srAfterEnd);
+
+    TCollectionType = (ctBag, ctSet, ctList, ctMap, ctIntegerMap, ctStringMap);
+
+    TCollectionFilterFunc = function (const Item: ICollectable): Boolean of object;
+    TCollectionCompareFunc = function (const Item1, Item2: ICollectable): Integer of object;
+
+    TSearchResult = record
+        ResultType: TSearchResultType;
+        Index: Integer;
+    end;
+
+    ICollectable = interface
+        ['{98998441-4C3E-11D7-8120-0002E3165EF8}']
+        function GetInstance: TObject;
+    end;
+
+    IEquatable = interface
+        ['{EAC823A7-0B90-11D7-8120-0002E3165EF8}']
+        function GetInstance: TObject;
+        function Equals(const Item: ICollectable): Boolean;
+    end;
+
+    IHashable = interface(IEquatable)
+        ['{98998440-4C3E-11D7-8120-0002E3165EF8}']
+        function HashCode: Integer;
+    end;
+
+    IComparable = interface(IEquatable)
+        ['{9F4C96C0-0CF0-11D7-8120-0002E3165EF8}']
+        function CompareTo(const Item: ICollectable): Integer;
+    end;
+
+    IMappable = interface(IEquatable)
+        ['{DAEC8CA0-0DBB-11D7-8120-0002E3165EF8}']
+        function GetKey: ICollectable;
+    end;
+
+    IStringMappable = interface(IEquatable)
+        ['{3CC61F40-5F92-11D7-8120-0002E3165EF8}']
+        function GetKey: String;
+    end;
+
+    IIntegerMappable = interface(IEquatable)
+        ['{774FC760-5F92-11D7-8120-0002E3165EF8}']
+        function GetKey: Integer;
+    end;
+
+    IComparator = interface
+        ['{1F20CD60-10FE-11D7-8120-0002E3165EF8}']
+        function GetInstance: TObject;
+        function Compare(const Item1, Item2: ICollectable): Integer;
+        function Equals(const Item1, Item2: ICollectable): Boolean; overload;
+        function Equals(const Comparator: IComparator): Boolean; overload;
+    end;
+
+    IFilter = interface
+        ['{27FE44C0-638E-11D7-8120-0002E3165EF8}']
+        function Accept(const Item: ICollectable): Boolean;
+    end;
+
+    IIterator = interface
+        ['{F6930500-1113-11D7-8120-0002E3165EF8}']
+        function GetAllowRemoval: Boolean;
+        function CurrentItem: ICollectable;
+        function EOF: Boolean;
+        function First: ICollectable;
+        function Next: ICollectable;
+        function Remove: Boolean;
+    end;
+
+    IMapIterator = interface(IIterator)
+        ['{848CC0E0-2A31-11D7-8120-0002E3165EF8}']
+        function CurrentKey: ICollectable;
+    end;
+
+    IIntegerMapIterator = interface(IIterator)
+        ['{C7169780-606C-11D7-8120-0002E3165EF8}']
+        function CurrentKey: Integer;
+    end;
+
+    IStringMapIterator = interface(IIterator)
+        ['{1345ED20-5F93-11D7-8120-0002E3165EF8}']
+        function CurrentKey: String;
+    end;
+
+    IAssociation = interface(ICollectable)
+        ['{556CD700-4DB3-11D7-8120-0002E3165EF8}']
+        function GetKey: ICollectable;
+        function GetValue: ICollectable;
+    end;
+
+    IIntegerAssociation = interface(ICollectable)
+        ['{ED954420-5F94-11D7-8120-0002E3165EF8}']
+        function GetKey: Integer;
+        function GetValue: ICollectable;
+    end;
+
+    IStringAssociation = interface(ICollectable)
+        ['{FB87D2A0-5F94-11D7-8120-0002E3165EF8}']
+        function GetKey: String;
+        function GetValue: ICollectable;
+    end;
+
+    IAssociationComparator = interface(IComparator)
+        ['{EA9BE6E0-A852-11D8-B93A-0002E3165EF8}']
+        function GetKeyComparator: IComparator;
+        procedure SetKeyComparator(Value: IComparator);
+        property KeyComparator: IComparator read GetKeyComparator write SetKeyComparator;
+    end;
+
+    IIntegerAssociationComparator = interface(IComparator)
+        ['{EA9BE6E1-A852-11D8-B93A-0002E3165EF8}']
+    end;
+
+    IStringAssociationComparator = interface(IComparator)
+        ['{EA9BE6E2-A852-11D8-B93A-0002E3165EF8}']
+    end;
+
+    ICollection = interface
+        ['{EAC823AC-0B90-11D7-8120-0002E3165EF8}']
+        function GetAsArray: TCollectableArray;
+        function GetCapacity: Integer;
+        procedure SetCapacity(Value: Integer);
+        function GetComparator: IComparator;
+        procedure SetComparator(const Value: IComparator);
+        function GetDuplicates: Boolean;
+        function GetFixedSize: Boolean;
+        function GetIgnoreErrors: TCollectionErrors;
+        procedure SetIgnoreErrors(Value: TCollectionErrors);
+        function GetInstance: TObject;
+        function GetIterator: IIterator; overload;
+        function GetIterator(const Filter: IFilter): IIterator; overload;
+        function GetIterator(FilterFunc: TCollectionFilterFunc): IIterator; overload;
+        function GetNaturalItemIID: TGUID;
+        function GetNaturalItemsOnly: Boolean;
+        function GetSize: Integer;
+        function GetType: TCollectionType;
+        function Add(const Item: ICollectable): Boolean; overload;
+        function Add(const ItemArray: array of ICollectable): Integer; overload;
+        function Add(const Collection: ICollection): Integer; overload;
+        function Clear: Integer;
+        function Clone: ICollection;
+        function Contains(const Item: ICollectable): Boolean; overload;
+        function Contains(const ItemArray: array of ICollectable): Boolean; overload;
+        function Contains(const Collection: ICollection): Boolean; overload;
+        function Equals(const Collection: ICollection): Boolean;
+        function Find(const Filter: IFilter): ICollectable; overload;
+        function Find(FilterFunc: TCollectionFilterFunc): ICollectable; overload;
+        function FindAll(const Filter: IFilter = nil): ICollection; overload;
+        function FindAll(FilterFunc: TCollectionFilterFunc): ICollection; overload;
+        function IsEmpty: Boolean;
+        function IsNaturalItem(const Item: ICollectable): Boolean;
+        function IsNilAllowed: Boolean;
+        function ItemAllowed(const Item: ICollectable): TCollectionError;
+        function ItemCount(const Item: ICollectable): Integer; overload;
+        function ItemCount(const ItemArray: array of ICollectable): Integer; overload;
+        function ItemCount(const Collection: ICollection): Integer; overload;
+        function Matching(const ItemArray: array of ICollectable): ICollection; overload;
+        function Matching(const Collection: ICollection): ICollection; overload;
+        function Remove(const Item: ICollectable): ICollectable; overload;
+        function Remove(const ItemArray: array of ICollectable): ICollection; overload;
+        function Remove(const Collection: ICollection): ICollection; overload;
+        function RemoveAll(const Item: ICollectable): ICollection; overload;
+        function RemoveAll(const ItemArray: array of ICollectable): ICollection; overload;
+        function RemoveAll(const Collection: ICollection): ICollection; overload;
+        function Retain(const ItemArray: array of ICollectable): ICollection; overload;
+        function Retain(const Collection: ICollection): ICollection; overload;
+        property AsArray: TCollectableArray read GetAsArray;
+        property Capacity: Integer read GetCapacity write SetCapacity;
+        property Comparator: IComparator read GetComparator write SetComparator;
+        property FixedSize: Boolean read GetFixedSize;
+        property IgnoreErrors: TCollectionErrors read GetIgnoreErrors write SetIgnoreErrors;
+        property NaturalItemIID: TGUID read GetNaturalItemIID;
+        property NaturalItemsOnly: Boolean read GetNaturalItemsOnly;
+        property Size: Integer read GetSize;
+    end;
+
+    IBag = interface(ICollection)
+        ['{C29C9560-2D59-11D7-8120-0002E3165EF8}']
+        function CloneAsBag: IBag;
+    end;
+
+    ISet = interface(ICollection)
+        ['{DD7888E2-0BB1-11D7-8120-0002E3165EF8}']
+        function CloneAsSet: ISet;
+        function Complement(const Universe: ISet): ISet;
+        function Intersect(const Set2: ISet): ISet;
+        function Union(const Set2: ISet): ISet;
+    end;
+
+    IList = interface(ICollection)
+        ['{EE81AB60-0B9F-11D7-8120-0002E3165EF8}']
+        function GetDuplicates: Boolean;
+        procedure SetDuplicates(Value: Boolean);
+        function GetItem(Index: Integer): ICollectable;
+        procedure SetItem(Index: Integer; const Item: ICollectable);
+        function GetSorted: Boolean;
+        procedure SetSorted(Value: Boolean);
+        function CloneAsList: IList;
+        function Delete(Index: Integer): ICollectable;
+        procedure Exchange(Index1, Index2: Integer);
+        function First: ICollectable;
+        function IndexOf(const Item: ICollectable): Integer;
+        function Insert(Index: Integer; const Item: ICollectable): Boolean; overload;
+        function Insert(Index: Integer; const ItemArray: array of ICollectable): Integer; overload;
+        function Insert(Index: Integer; const Collection: ICollection): Integer; overload;
+        function Last: ICollectable;
+        procedure Sort(const Comparator: IComparator); overload;
+        procedure Sort(CompareFunc: TCollectionCompareFunc); overload;
+        property Duplicates: Boolean read GetDuplicates write SetDuplicates;
+        property Items[Index: Integer]: ICollectable read GetItem write SetItem; default;
+        property Sorted: Boolean read GetSorted write SetSorted;
+    end;
+
+    IMap = interface(ICollection)
+        ['{AD458280-2A6B-11D7-8120-0002E3165EF8}']
+        function GetItem(const Key: ICollectable): ICollectable;
+        procedure SetItem(const Key, Item: ICollectable);
+        function GetKeyComparator: IComparator;
+        procedure SetKeyComparator(const Value: IComparator);
+        function GetKeyIterator: IIterator;
+        function GetKeys: ISet;
+        function GetMapIterator: IMapIterator;
+        function GetMapIteratorByKey(const Filter: IFilter): IMapIterator; overload;
+        function GetMapIteratorByKey(FilterFunc: TCollectionFilterFunc): IMapIterator; overload;
+        function GetNaturalKeyIID: TGUID;
+        function GetNaturalKeysOnly: Boolean;
+        function GetValues: ICollection;
+        function CloneAsMap: IMap;
+        function ContainsKey(const Key: ICollectable): Boolean; overload;
+        function ContainsKey(const KeyArray: array of ICollectable): Boolean; overload;
+        function ContainsKey(const Collection: ICollection): Boolean; overload;
+        function Get(const Key: ICollectable): ICollectable;
+        function IsNaturalKey(const Key: ICollectable): Boolean;
+        function KeyAllowed(const Key: ICollectable): TCollectionError;
+        function MatchingKey(const KeyArray: array of ICollectable): ICollection; overload;
+        function MatchingKey(const Collection: ICollection): ICollection; overload;
+        function Put(const Item: ICollectable): ICollectable; overload;
+        function Put(const Key, Item: ICollectable): ICollectable; overload;
+        function Put(const ItemArray: array of ICollectable): ICollection; overload;
+        function Put(const Collection: ICollection): ICollection; overload;
+        function Put(const Map: IMap): ICollection; overload;
+        function RemoveKey(const Key: ICollectable): ICollectable; overload;
+        function RemoveKey(const KeyArray: array of ICollectable): ICollection; overload;
+        function RemoveKey(const Collection: ICollection): ICollection; overload;
+        function RetainKey(const KeyArray: array of ICollectable): ICollection; overload;
+        function RetainKey(const Collection: ICollection): ICollection; overload;
+        property KeyComparator: IComparator read GetKeyComparator write SetKeyComparator;
+        property Items[const Key: ICollectable]: ICollectable read GetItem write SetItem; default;
+        property NaturalKeyIID: TGUID read GetNaturalKeyIID;
+        property NaturalKeysOnly: Boolean read GetNaturalKeysOnly;
+    end;
+
+    IIntegerMap = interface(ICollection)
+        ['{93DBA9A0-606C-11D7-8120-0002E3165EF8}']
+        function GetItem(const Key: Integer): ICollectable;
+        procedure SetItem(const Key: Integer; const Item: ICollectable);
+        function GetKeys: ISet;
+        function GetMapIterator: IIntegerMapIterator;
+        function GetValues: ICollection;
+        function CloneAsIntegerMap: IIntegerMap;
+        function ContainsKey(const Key: Integer): Boolean; overload;
+        function ContainsKey(const KeyArray: array of Integer): Boolean; overload;
+        function Get(const Key: Integer): ICollectable;
+        function Put(const Item: ICollectable): ICollectable; overload;
+        function Put(const Key: Integer; const Item: ICollectable): ICollectable; overload;
+        function Put(const ItemArray: array of ICollectable): ICollection; overload;
+        function Put(const Collection: ICollection): ICollection; overload;
+        function Put(const Map: IIntegerMap): ICollection; overload;
+        function RemoveKey(const Key: Integer): ICollectable; overload;
+        function RemoveKey(const KeyArray: array of Integer): ICollection; overload;
+        function RetainKey(const KeyArray: array of Integer): ICollection; overload;
+        property Items[const Key: Integer]: ICollectable read GetItem write SetItem; default;
+    end;
+
+    IStringMap = interface(ICollection)
+        ['{20531A20-5F92-11D7-8120-0002E3165EF8}']
+        function GetItem(const Key: String): ICollectable;
+        procedure SetItem(const Key: String; const Item: ICollectable);
+        function GetKeys: ISet;
+        function GetMapIterator: IStringMapIterator;
+        function GetValues: ICollection;
+        function CloneAsStringMap: IStringMap;
+        function ContainsKey(const Key: String): Boolean; overload;
+        function ContainsKey(const KeyArray: array of String): Boolean; overload;
+        function Get(const Key: String): ICollectable;
+        function Put(const Item: ICollectable): ICollectable; overload;
+        function Put(const Key: String; const Item: ICollectable): ICollectable; overload;
+        function Put(const ItemArray: array of ICollectable): ICollection; overload;
+        function Put(const Collection: ICollection): ICollection; overload;
+        function Put(const Map: IStringMap): ICollection; overload;
+        function RemoveKey(const Key: String): ICollectable; overload;
+        function RemoveKey(const KeyArray: array of String): ICollection; overload;
+        function RetainKey(const KeyArray: array of String): ICollection; overload;
+        property Items[const Key: String]: ICollectable read GetItem write SetItem; default;
+    end;
+
+    TCollectionPosition = class
+    private
+        FFound: Boolean;
+    public
+        constructor Create(Found: Boolean);
+        property Found: Boolean read FFound;
+    end;
+
+    TAbstractComparator = class(TInterfacedObject, IComparator)
+    public
+        class function GetDefaultComparator: IComparator;
+        class function GetNaturalComparator: IComparator;
+        class function GetReverseNaturalComparator: IComparator;
+        function GetInstance: TObject;
+        function Compare(const Item1, Item2: ICollectable): Integer; virtual; abstract;
+        function Equals(const Item1, Item2: ICollectable): Boolean; overload; virtual; abstract;
+        function Equals(const Comparator: IComparator): Boolean; overload; virtual;
+    end;
+
+    TDefaultComparator = class(TAbstractComparator)
+    protected
+        constructor Create;
+    public
+        function Compare(const Item1, Item2: ICollectable): Integer; override;
+        function Equals(const Item1, Item2: ICollectable): Boolean; override;
+    end;
+
+    TNaturalComparator = class(TAbstractComparator)
+    protected
+        constructor Create;
+    public
+        function Compare(const Item1, Item2: ICollectable): Integer; override;
+        function Equals(const Item1, Item2: ICollectable): Boolean; override;
+    end;
+
+    TReverseNaturalComparator = class(TAbstractComparator)
+    protected
+        constructor Create;
+    public
+        function Compare(const Item1, Item2: ICollectable): Integer; override;
+        function Equals(const Item1, Item2: ICollectable): Boolean; override;
+    end;
+
+    TAssociation = class(TInterfacedObject, ICollectable, IAssociation)
+    private
+        FKey: ICollectable;
+        FValue: ICollectable;
+    public
+        constructor Create(const Key, Value: ICollectable); virtual;
+        destructor Destroy; override;
+        function GetInstance: TObject; virtual;
+        function GetKey: ICollectable;
+        function GetValue: ICollectable;
+    end;
+
+    TIntegerAssociation = class(TInterfacedObject, ICollectable, IIntegerAssociation)
+    private
+        FKey: Integer;
+        FValue: ICollectable;
+    public
+        constructor Create(const Key: Integer; const Value: ICollectable); virtual;
+        destructor Destroy; override;
+        function GetInstance: TObject; virtual;
+        function GetKey: Integer;
+        function GetValue: ICollectable;
+    end;
+
+    TStringAssociation = class(TInterfacedObject, ICollectable, IStringAssociation)
+    private
+        FKey: String;
+        FValue: ICollectable;
+    public
+        constructor Create(const Key: String; const Value: ICollectable); virtual;
+        destructor Destroy; override;
+        function GetInstance: TObject; virtual;
+        function GetKey: String;
+        function GetValue: ICollectable;
+    end;
+
+    TAssociationComparator = class(TAbstractComparator, IAssociationComparator)
+    private
+        FKeyComparator: IComparator;
+    public
+        constructor Create(NaturalKeys: Boolean = false);
+        destructor Destroy; override;
+        function GetKeyComparator: IComparator;
+        procedure SetKeyComparator(Value: IComparator);
+        function Compare(const Item1, Item2: ICollectable): Integer; override;
+        function Equals(const Item1, Item2: ICollectable): Boolean; override;
+        property KeyComparator: IComparator read GetKeyComparator write SetKeyComparator;
+    end;
+
+    TIntegerAssociationComparator = class(TAbstractComparator, IIntegerAssociationComparator)
+    public
+        constructor Create;
+        destructor Destroy; override;
+        function Compare(const Item1, Item2: ICollectable): Integer; override;
+        function Equals(const Item1, Item2: ICollectable): Boolean; override;
+    end;
+
+    TStringAssociationComparator = class(TAbstractComparator, IStringAssociationComparator)
+    public
+        constructor Create;
+        destructor Destroy; override;
+        function Compare(const Item1, Item2: ICollectable): Integer; override;
+        function Equals(const Item1, Item2: ICollectable): Boolean; override;
+    end;
+
+
+
+    TAbstractCollection = class(TInterfacedObject, ICollection)
+    private
+        FCreated: Boolean;          // Required to avoid passing destroyed object reference to exception
+        FComparator: IComparator;
+        FIgnoreErrors: TCollectionErrors;
+        FNaturalItemsOnly: Boolean;
+    protected
+        procedure CollectionError(ErrorType: TCollectionError);
+        procedure InitFrom(const Collection: ICollection); overload; virtual;
+        function TrueAdd(const Item: ICollectable): Boolean; virtual; abstract;
+        procedure TrueClear; virtual; abstract;
+        function TrueContains(const Item: ICollectable): Boolean; virtual; abstract;
+        function TrueItemCount(const Item: ICollectable): Integer; virtual;
+        function TrueRemove(const Item: ICollectable): ICollectable; virtual; abstract;
+        function TrueRemoveAll(const Item: ICollectable): ICollection; virtual; abstract;
+    public
+        constructor Create; overload; virtual;
+        constructor Create(NaturalItemsOnly: Boolean); overload; virtual;
+        constructor Create(const ItemArray: array of ICollectable); overload; virtual;
+        constructor Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean); overload; virtual;
+        constructor Create(const Collection: ICollection); overload; virtual;
+        destructor Destroy; override;
+        class function GetAlwaysNaturalItems: Boolean; virtual;
+        function GetAsArray: TCollectableArray; virtual;
+        function GetCapacity: Integer; virtual; abstract;
+        procedure SetCapacity(Value: Integer); virtual; abstract;
+        function GetComparator: IComparator; virtual;
+        procedure SetComparator(const Value: IComparator); virtual;
+        function GetDuplicates: Boolean; virtual;
+        function GetFixedSize: Boolean; virtual;
+        function GetIgnoreErrors: TCollectionErrors;
+        procedure SetIgnoreErrors(Value: TCollectionErrors);
+        function GetInstance: TObject;
+        function GetIterator: IIterator; overload; virtual; abstract;
+        function GetIterator(const Filter: IFilter): IIterator; overload; virtual;
+        function GetIterator(FilterFunc: TCollectionFilterFunc): IIterator; overload; virtual;
+        function GetNaturalItemIID: TGUID; virtual; abstract;
+        function GetNaturalItemsOnly: Boolean; virtual;
+        function GetSize: Integer; virtual; abstract;
+        function GetType: TCollectionType; virtual; abstract;
+        function Add(const Item: ICollectable): Boolean; overload; virtual;
+        function Add(const ItemArray: array of ICollectable): Integer; overload; virtual;
+        function Add(const Collection: ICollection): Integer; overload; virtual;
+        procedure AfterConstruction; override;
+        procedure BeforeDestruction; override;
+        function Clear: Integer; virtual;
+        function Clone: ICollection; virtual;
+        function Contains(const Item: ICollectable): Boolean; overload; virtual;
+        function Contains(const ItemArray: array of ICollectable): Boolean; overload; virtual;
+        function Contains(const Collection: ICollection): Boolean; overload; virtual;
+        function Equals(const Collection: ICollection): Boolean; virtual;
+        function Find(const Filter: IFilter): ICollectable; overload; virtual;
+        function Find(FilterFunc: TCollectionFilterFunc): ICollectable; overload; virtual;
+        function FindAll(const Filter: IFilter): ICollection; overload; virtual;
+        function FindAll(FilterFunc: TCollectionFilterFunc): ICollection; overload; virtual;
+        function IsEmpty: Boolean; virtual;
+        function IsNaturalItem(const Item: ICollectable): Boolean; virtual;
+        function IsNilAllowed: Boolean; virtual; abstract;
+        function ItemAllowed(const Item: ICollectable): TCollectionError; virtual;
+        function ItemCount(const Item: ICollectable): Integer; overload; virtual;
+        function ItemCount(const ItemArray: array of ICollectable): Integer; overload; virtual;
+        function ItemCount(const Collection: ICollection): Integer; overload; virtual;
+        function Matching(const ItemArray: array of ICollectable): ICollection; overload; virtual;
+        function Matching(const Collection: ICollection): ICollection; overload; virtual;
+        function Remove(const Item: ICollectable): ICollectable; overload; virtual;
+        function Remove(const ItemArray: array of ICollectable): ICollection; overload; virtual;
+        function Remove(const Collection: ICollection): ICollection; overload; virtual;
+        function RemoveAll(const Item: ICollectable): ICollection; overload; virtual;
+        function RemoveAll(const ItemArray: array of ICollectable): ICollection; overload; virtual;
+        function RemoveAll(const Collection: ICollection): ICollection; overload; virtual;
+        function Retain(const ItemArray: array of ICollectable): ICollection; overload; virtual;
+        function Retain(const Collection: ICollection): ICollection; overload; virtual;
+        property AsArray: TCollectableArray read GetAsArray;
+        property Capacity: Integer read GetCapacity write SetCapacity;
+        property Comparator: IComparator read GetComparator write SetComparator;
+        property FixedSize: Boolean read GetFixedSize;
+        property IgnoreErrors: TCollectionErrors read GetIgnoreErrors write SetIgnoreErrors;
+        property NaturalItemIID: TGUID read GetNaturalItemIID;
+        property NaturalItemsOnly: Boolean read GetNaturalItemsOnly;
+        property Size: Integer read GetSize;
+    end;
+
+    TAbstractBag = class(TAbstractCollection, IBag)
+    public
+        function CloneAsBag: IBag; virtual;
+        function GetNaturalItemIID: TGUID; override;
+        function GetType: TCollectionType; override;
+        function IsNilAllowed: Boolean; override;
+    end;
+
+    TAbstractSet = class (TAbstractCollection, ISet)
+    protected
+        function GetPosition(const Item: ICollectable): TCollectionPosition; virtual; abstract;
+        function TrueAdd(const Item: ICollectable): Boolean; override;
+        procedure TrueAdd2(Position: TCollectionPosition; const Item: ICollectable); virtual; abstract;
+        function TrueContains(const Item: ICollectable): Boolean; override;
+        function TrueGet(Position: TCollectionPosition): ICollectable; virtual; abstract;
+        function TrueRemove(const Item: ICollectable): ICollectable; override;
+        procedure TrueRemove2(Position: TCollectionPosition); virtual; abstract;
+        function TrueRemoveAll(const Item: ICollectable): ICollection; override;
+    public
+        function GetDuplicates: Boolean; override;
+        function GetNaturalItemIID: TGUID; override;
+        function GetType: TCollectionType; override;
+        function CloneAsSet: ISet; virtual;
+        function Complement(const Universe: ISet): ISet; overload; virtual;
+        function Intersect(const Set2: ISet): ISet; overload; virtual;
+        function IsNilAllowed: Boolean; override;
+        function Union(const Set2: ISet): ISet; overload; virtual;
+    end;
+
+    TAbstractList = class(TAbstractCollection, IList)
+    private
+        FDuplicates: Boolean;
+        FSorted: Boolean;
+    protected
+        function BinarySearch(const Item: ICollectable): TSearchResult; virtual;
+        procedure InitFrom(const Collection: ICollection); override;
+        procedure QuickSort(Lo, Hi: Integer; const Comparator: IComparator); overload; virtual;
+        procedure QuickSort(Lo, Hi: Integer; CompareFunc: TCollectionCompareFunc); overload; virtual;
+        function SequentialSearch(const Item: ICollectable; const SearchComparator: IComparator = nil): TSearchResult; virtual;
+        function TrueContains(const Item: ICollectable): Boolean; override;
+        function TrueGetItem(Index: Integer): ICollectable; virtual; abstract;
+        procedure TrueSetItem(Index: Integer; const Item: ICollectable); virtual; abstract;
+        function TrueAdd(const Item: ICollectable): Boolean; override;
+        procedure TrueAppend(const Item: ICollectable); virtual; abstract;
+        function TrueDelete(Index: Integer): ICollectable; virtual; abstract;
+        procedure TrueInsert(Index: Integer; const Item: ICollectable); virtual; abstract;
+        function TrueItemCount(const Item: ICollectable): Integer; override;
+        function TrueRemove(const Item: ICollectable): ICollectable; override;
+        function TrueRemoveAll(const Item: ICollectable): ICollection; override;
+    public
+        constructor Create(NaturalItemsOnly: Boolean); override;
+        function GetDuplicates: Boolean; override;
+        procedure SetDuplicates(Value: Boolean); virtual;
+        function GetItem(Index: Integer): ICollectable; virtual;
+        procedure SetItem(Index: Integer; const Item: ICollectable); virtual;
+        function GetIterator: IIterator; override;
+        function GetNaturalItemIID: TGUID; override;
+        function GetSorted: Boolean; virtual;
+        procedure SetSorted(Value: Boolean); virtual;
+        function GetType: TCollectionType; override;
+        function CloneAsList: IList; virtual;
+        function Delete(Index: Integer): ICollectable; virtual;
+        procedure Exchange(Index1, Index2: Integer); virtual;
+        function First: ICollectable; virtual;
+        function IndexOf(const Item: ICollectable): Integer; virtual;
+        function Insert(Index: Integer; const Item: ICollectable): Boolean; overload; virtual;
+        function Insert(Index: Integer; const ItemArray: array of ICollectable): Integer; overload; virtual;
+        function Insert(Index: Integer; const Collection: ICollection): Integer; overload; virtual;
+        function IsNilAllowed: Boolean; override;
+        function Last: ICollectable; virtual;
+        function Search(const Item: ICollectable; const SearchComparator: IComparator = nil): TSearchResult; virtual;
+        procedure Sort(const SortComparator: IComparator = nil); overload; virtual;
+        procedure Sort(CompareFunc: TCollectionCompareFunc); overload; virtual;
+        property Duplicates: Boolean read GetDuplicates write SetDuplicates;
+        property Items[Index: Integer]: ICollectable read GetItem write SetItem; default;
+        property Sorted: Boolean read GetSorted write SetSorted;
+    end;
+
+    TAbstractMap = class(TAbstractCollection, IMap)
+    private
+        FAssociationComparator: IAssociationComparator;
+        FKeyComparator: IComparator;
+        FNaturalKeysOnly: Boolean;
+    protected
+        function GetAssociationIterator: IMapIterator; virtual; abstract;
+        function GetKeyPosition(const Key: ICollectable): TCollectionPosition; virtual; abstract;
+        procedure InitFrom(const Collection: ICollection); override;
+        function TrueAdd(const Item: ICollectable): Boolean; override;
+        function TrueContains(const Item: ICollectable): Boolean; override;
+        function TrueGet(Position: TCollectionPosition): IAssociation; virtual; abstract;
+        function TruePut(Position: TCollectionPosition; const Association: IAssociation): IAssociation; virtual; abstract;
+        function TrueRemove(const Item: ICollectable): ICollectable; override;
+        function TrueRemove2(Position: TCollectionPosition): IAssociation; virtual; abstract;
+        function TrueRemoveAll(const Item: ICollectable): ICollection; override;
+        property AssociationComparator: IAssociationComparator read FAssociationComparator;
+    public
+        constructor Create; override;
+        constructor Create(NaturalItemsOnly: Boolean); override;
+        constructor Create(NaturalItemsOnly: Boolean; NaturalKeysOnly: Boolean); overload; virtual;
+        constructor Create(const ItemArray: array of ICollectable); overload; override;
+        constructor Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean); overload; override;
+        constructor Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean; NaturalKeysOnly: Boolean); overload; virtual;
+        constructor Create(const KeyArray, ItemArray: array of ICollectable); overload; virtual;
+        constructor Create(const KeyArray, ItemArray: array of ICollectable; NaturalItemsOnly: Boolean); overload; virtual;
+        constructor Create(const KeyArray, ItemArray: array of ICollectable; NaturalItemsOnly: Boolean; NaturalKeysOnly: Boolean); overload; virtual;
+//      Don't use this parameter signature as it hits a compiler bug in D5.
+//        constructor Create(const KeyArray, ItemArray: TCollectableArray; NaturalItemsOnly: Boolean = false; NaturalKeysOnly: Boolean = true); overload; virtual;
+        constructor Create(const Map: IMap); overload; virtual;
+        destructor Destroy; override;
+        class function GetAlwaysNaturalKeys: Boolean; virtual;
+        function GetItem(const Key: ICollectable): ICollectable; virtual;
+        procedure SetItem(const Key, Item: ICollectable); virtual;
+        function GetIterator: IIterator; override;
+        function GetKeyComparator: IComparator; virtual;
+        procedure SetKeyComparator(const Value: IComparator); virtual;
+        function GetKeyIterator: IIterator; virtual;
+        function GetKeys: ISet; virtual;
+        function GetMapIterator: IMapIterator; virtual;
+        function GetMapIteratorByKey(const Filter: IFilter): IMapIterator; overload; virtual;
+        function GetMapIteratorByKey(FilterFunc: TCollectionFilterFunc): IMapIterator; overload; virtual;
+        function GetNaturalItemIID: TGUID; override;
+        function GetNaturalKeyIID: TGUID; virtual;
+        function GetNaturalKeysOnly: Boolean; virtual;
+        function GetType: TCollectionType; override;
+        function GetValues: ICollection; virtual;
+        function Clone: ICollection; override;
+        function CloneAsMap: IMap; virtual;
+        function ContainsKey(const Key: ICollectable): Boolean; overload; virtual;
+        function ContainsKey(const KeyArray: array of ICollectable): Boolean; overload; virtual;
+        function ContainsKey(const Collection: ICollection): Boolean; overload; virtual;
+        function Get(const Key: ICollectable): ICollectable; virtual;
+        function KeyAllowed(const Key: ICollectable): TCollectionError; virtual;
+        function IsNaturalKey(const Key: ICollectable): Boolean; virtual;
+        function IsNilAllowed: Boolean; override;
+        function MatchingKey(const KeyArray: array of ICollectable): ICollection; overload; virtual;
+        function MatchingKey(const Collection: ICollection): ICollection; overload; virtual;
+        function Put(const Item: ICollectable): ICollectable; overload; virtual;
+        function Put(const Key, Item: ICollectable): ICollectable; overload; virtual;
+        function Put(const ItemArray: array of ICollectable): ICollection; overload; virtual;
+        function Put(const Collection: ICollection): ICollection; overload; virtual;
+        function Put(const Map: IMap): ICollection; overload; virtual;
+        function RemoveKey(const Key: ICollectable): ICollectable; overload; virtual;
+        function RemoveKey(const KeyArray: array of ICollectable): ICollection; overload; virtual;
+        function RemoveKey(const Collection: ICollection): ICollection; overload; virtual;
+        function RetainKey(const KeyArray: array of ICollectable): ICollection; overload; virtual;
+        function RetainKey(const Collection: ICollection): ICollection; overload; virtual;
+        property KeyComparator: IComparator read GetKeyComparator write SetKeyComparator;
+        property Items[const Key: ICollectable]: ICollectable read GetItem write SetItem; default;
+        property NaturalKeyIID: TGUID read GetNaturalKeyIID;
+        property NaturalKeysOnly: Boolean read GetNaturalKeysOnly;
+    end;
+
+    TAbstractIntegerMap = class(TAbstractCollection, IIntegerMap)
+    private
+        FAssociationComparator: IIntegerAssociationComparator;
+    protected
+        function GetAssociationIterator: IIntegerMapIterator; virtual; abstract;
+        function GetKeyPosition(const Key: Integer): TCollectionPosition; virtual; abstract;
+        function TrueAdd(const Item: ICollectable): Boolean; override;
+        function TrueContains(const Item: ICollectable): Boolean; override;
+        function TrueGet(Position: TCollectionPosition): IIntegerAssociation; virtual; abstract;
+        function TruePut(Position: TCollectionPosition; const Association: IIntegerAssociation): IIntegerAssociation; virtual; abstract;
+        function TrueRemove(const Item: ICollectable): ICollectable; override;
+        function TrueRemove2(Position: TCollectionPosition): IIntegerAssociation; virtual; abstract;
+        function TrueRemoveAll(const Item: ICollectable): ICollection; override;
+        property AssociationComparator: IIntegerAssociationComparator read FAssociationComparator;
+    public
+        constructor Create(NaturalItemsOnly: Boolean); override;
+        constructor Create(const ItemArray: array of ICollectable); overload; override;
+        constructor Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean); overload; override;
+        constructor Create(const KeyArray: array of Integer; const ItemArray: array of ICollectable); overload; virtual;
+        constructor Create(const KeyArray: array of Integer; const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean); overload; virtual;
+        constructor Create(const Map: IIntegerMap); overload; virtual;
+        destructor Destroy; override;
+        function GetItem(const Key: Integer): ICollectable; virtual;
+        procedure SetItem(const Key: Integer; const Item: ICollectable); virtual;
+        function GetIterator: IIterator; override;
+        function GetKeys: ISet; virtual;
+        function GetMapIterator: IIntegerMapIterator; virtual;
+        function GetNaturalItemIID: TGUID; override;
+        function GetType: TCollectionType; override;
+        function GetValues: ICollection; virtual;
+        function Clone: ICollection; override;
+        function CloneAsIntegerMap: IIntegerMap; virtual;
+        function ContainsKey(const Key: Integer): Boolean; overload; virtual;
+        function ContainsKey(const KeyArray: array of Integer): Boolean; overload; virtual;
+        function Get(const Key: Integer): ICollectable; virtual;
+        function IsNilAllowed: Boolean; override;
+        function Put(const Item: ICollectable): ICollectable; overload; virtual;
+        function Put(const Key: Integer; const Item: ICollectable): ICollectable; overload; virtual;
+        function Put(const ItemArray: array of ICollectable): ICollection; overload; virtual;
+        function Put(const Collection: ICollection): ICollection; overload; virtual;
+        function Put(const Map: IIntegerMap): ICollection; overload; virtual;
+        function RemoveKey(const Key: Integer): ICollectable; overload; virtual;
+        function RemoveKey(const KeyArray: array of Integer): ICollection; overload; virtual;
+        function RetainKey(const KeyArray: array of Integer): ICollection; overload; virtual;
+        property Items[const Key: Integer]: ICollectable read GetItem write SetItem; default;
+    end;
+
+    TAbstractStringMap = class(TAbstractCollection, IStringMap)
+    private
+        FAssociationComparator: IStringAssociationComparator;
+    protected
+        function GetAssociationIterator: IStringMapIterator; virtual; abstract;
+        function GetKeyPosition(const Key: String): TCollectionPosition; virtual; abstract;
+        function TrueAdd(const Item: ICollectable): Boolean; override;
+        function TrueContains(const Item: ICollectable): Boolean; override;
+        function TrueGet(Position: TCollectionPosition): IStringAssociation; virtual; abstract;
+        function TruePut(Position: TCollectionPosition; const Association: IStringAssociation): IStringAssociation; virtual; abstract;
+        function TrueRemove(const Item: ICollectable): ICollectable; override;
+        function TrueRemove2(Position: TCollectionPosition): IStringAssociation; virtual; abstract;
+        function TrueRemoveAll(const Item: ICollectable): ICollection; override;
+        property AssociationComparator: IStringAssociationComparator read FAssociationComparator;
+    public
+        constructor Create(NaturalItemsOnly: Boolean); override;
+        constructor Create(const ItemArray: array of ICollectable); overload; override;
+        constructor Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean); overload; override;
+        constructor Create(const KeyArray: array of String; const ItemArray: array of ICollectable); overload; virtual;
+        constructor Create(const KeyArray: array of String; const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean); overload; virtual;
+        constructor Create(const Map: IStringMap); overload; virtual;
+        destructor Destroy; override;
+        function GetItem(const Key: String): ICollectable; virtual;
+        procedure SetItem(const Key: String; const Item: ICollectable); virtual;
+        function GetIterator: IIterator; override;
+        function GetKeys: ISet; virtual;
+        function GetMapIterator: IStringMapIterator; virtual;
+        function GetNaturalItemIID: TGUID; override;
+        function GetType: TCollectionType; override;
+        function GetValues: ICollection; virtual;
+        function Clone: ICollection; override;
+        function CloneAsStringMap: IStringMap; virtual;
+        function ContainsKey(const Key: String): Boolean; overload; virtual;
+        function ContainsKey(const KeyArray: array of String): Boolean; overload; virtual;
+        function Get(const Key: String): ICollectable; virtual;
+        function IsNilAllowed: Boolean; override;
+        function Put(const Item: ICollectable): ICollectable; overload; virtual;
+        function Put(const Key: String; const Item: ICollectable): ICollectable; overload; virtual;
+        function Put(const ItemArray: array of ICollectable): ICollection; overload; virtual;
+        function Put(const Collection: ICollection): ICollection; overload; virtual;
+        function Put(const Map: IStringMap): ICollection; overload; virtual;
+        function RemoveKey(const Key: String): ICollectable; overload; virtual;
+        function RemoveKey(const KeyArray: array of String): ICollection; overload; virtual;
+        function RetainKey(const KeyArray: array of String): ICollection; overload; virtual;
+        property Items[const Key: String]: ICollectable read GetItem write SetItem; default;
+    end;
+
+    TAbstractCollectionClass = class of TAbstractCollection;
+    TAbstractBagClass = class of TAbstractBag;
+    TAbstractSetClass = class of TAbstractSet;
+    TAbstractListClass = class of TAbstractList;
+    TAbstractMapClass = class of TAbstractMap;
+    TAbstractIntegerMapClass = class of TAbstractIntegerMap;
+    TAbstractStringMapClass = class of TAbstractStringMap;
+
+    TAbstractIterator = class(TInterfacedObject, IIterator)
+    private
+        FAllowRemoval: Boolean;
+        FEOF: Boolean;
+        FItem: ICollectable;
+    protected
+        constructor Create(AllowRemoval: Boolean = true);
+        function TrueFirst: ICollectable; virtual; abstract;
+        function TrueNext: ICollectable; virtual; abstract;
+        procedure TrueRemove; virtual; abstract;
+    public
+        procedure AfterConstruction; override;
+        function GetAllowRemoval: Boolean; virtual;
+        function CurrentItem: ICollectable; virtual;
+        function EOF: Boolean; virtual;
+        function First: ICollectable; virtual;
+        function Next: ICollectable; virtual;
+        function Remove: Boolean; virtual;
+        property AllowRemoval: Boolean read GetAllowRemoval;
+    end;
+
+    TAbstractListIterator = class(TAbstractIterator)
+    private
+        FCollection: TAbstractList;
+        FIndex: Integer;
+    protected
+        constructor Create(Collection: TAbstractList);
+        function TrueFirst: ICollectable; override;
+        function TrueNext: ICollectable; override;
+        procedure TrueRemove; override;
+    end;
+
+    TAbstractMapIterator = class(TAbstractIterator, IMapIterator)
+    public
+        function CurrentKey: ICollectable; virtual; abstract;
+    end;
+
+    TAbstractAssociationIterator = class(TInterfacedObject, IIterator, IMapIterator)
+    private
+        FAllowRemoval: Boolean;
+        FEOF: Boolean;
+        FAssociation: IAssociation;
+    protected
+        constructor Create(AllowRemoval: Boolean = true);
+        function TrueFirst: IAssociation; virtual; abstract;
+        function TrueNext: IAssociation; virtual; abstract;
+        procedure TrueRemove; virtual; abstract;
+    public
+        procedure AfterConstruction; override;
+        function GetAllowRemoval: Boolean; virtual;
+        function CurrentKey: ICollectable; virtual;
+        function CurrentItem: ICollectable; virtual;
+        function EOF: Boolean; virtual;
+        function First: ICollectable; virtual;
+        function Next: ICollectable; virtual;
+        function Remove: Boolean; virtual;
+        property AllowRemoval: Boolean read GetAllowRemoval;
+    end;
+
+    TAbstractIntegerAssociationIterator = class(TInterfacedObject, IIterator, IIntegerMapIterator)
+    private
+        FAllowRemoval: Boolean;
+        FEOF: Boolean;
+        FAssociation: IIntegerAssociation;
+    protected
+        constructor Create(AllowRemoval: Boolean = true);
+        function TrueFirst: IIntegerAssociation; virtual; abstract;
+        function TrueNext: IIntegerAssociation; virtual; abstract;
+        procedure TrueRemove; virtual; abstract;
+    public
+        procedure AfterConstruction; override;
+        function GetAllowRemoval: Boolean; virtual;
+        function CurrentKey: Integer; virtual;
+        function CurrentItem: ICollectable; virtual;
+        function EOF: Boolean; virtual;
+        function First: ICollectable; virtual;
+        function Next: ICollectable; virtual;
+        function Remove: Boolean; virtual;
+        property AllowRemoval: Boolean read GetAllowRemoval;
+    end;
+
+    TAbstractStringAssociationIterator = class(TInterfacedObject, IIterator, IStringMapIterator)
+    private
+        FAllowRemoval: Boolean;
+        FEOF: Boolean;
+        FAssociation: IStringAssociation;
+    protected
+        constructor Create(AllowRemoval: Boolean = true);
+        function TrueFirst: IStringAssociation; virtual; abstract;
+        function TrueNext: IStringAssociation; virtual; abstract;
+        procedure TrueRemove; virtual; abstract;
+    public
+        procedure AfterConstruction; override;
+        function GetAllowRemoval: Boolean; virtual;
+        function CurrentKey: String; virtual;
+        function CurrentItem: ICollectable; virtual;
+        function EOF: Boolean; virtual;
+        function First: ICollectable; virtual;
+        function Next: ICollectable; virtual;
+        function Remove: Boolean; virtual;
+        property AllowRemoval: Boolean read GetAllowRemoval;
+    end;
+
+    TAssociationIterator = class(TAbstractIterator, IMapIterator)
+    private
+        FIterator: IIterator;
+    protected
+        function TrueFirst: ICollectable; override;
+        function TrueNext: ICollectable; override;
+        procedure TrueRemove; override;
+    public
+        constructor Create(const Iterator: IIterator);
+        destructor Destroy; override;
+        function CurrentItem: ICollectable; override;
+        function CurrentKey: ICollectable; virtual;
+    end;
+
+    TAssociationKeyIterator = class(TAbstractIterator)
+    private
+        FIterator: IMapIterator;
+    protected
+        function TrueFirst: ICollectable; override;
+        function TrueNext: ICollectable; override;
+        procedure TrueRemove; override;
+    public
+        constructor Create(const Iterator: IMapIterator);
+        destructor Destroy; override;
+    end;
+
+    TAbstractFilter = class(TInterfacedObject, IFilter)
+    public
+        function Accept(const Item: ICollectable): Boolean; virtual; abstract;
+    end;
+
+    TFilterIterator = class(TAbstractIterator)
+    private
+        FIterator: IIterator;
+        FFilter: IFilter;
+    protected
+        function TrueFirst: ICollectable; override;
+        function TrueNext: ICollectable; override;
+        procedure TrueRemove; override;
+    public
+        constructor Create(const Iterator: IIterator; const Filter: IFilter; AllowRemoval: Boolean = true); virtual;
+        destructor Destroy; override;
+    end;
+
+    TFilterFuncIterator = class(TAbstractIterator)
+    private
+        FIterator: IIterator;
+        FFilterFunc: TCollectionFilterFunc;
+    protected
+        function TrueFirst: ICollectable; override;
+        function TrueNext: ICollectable; override;
+        procedure TrueRemove; override;
+    public
+        constructor Create(const Iterator: IIterator; FilterFunc: TCollectionFilterFunc; AllowRemoval: Boolean = true); virtual;
+        destructor Destroy; override;
+    end;
+
+    TKeyFilterMapIterator = class(TAbstractMapIterator)
+    private
+        FIterator: IMapIterator;
+        FFilter: IFilter;
+    protected
+        function TrueFirst: ICollectable; override;
+        function TrueNext: ICollectable; override;
+        procedure TrueRemove; override;
+    public
+        constructor Create(const Iterator: IMapIterator; const Filter: IFilter; AllowRemoval: Boolean = true); virtual;
+        destructor Destroy; override;
+        function CurrentKey: ICollectable; override;
+    end;
+
+    TKeyFilterFuncMapIterator = class(TAbstractMapIterator)
+    private
+        FIterator: IMapIterator;
+        FFilterFunc: TCollectionFilterFunc;
+    protected
+        function TrueFirst: ICollectable; override;
+        function TrueNext: ICollectable; override;
+        procedure TrueRemove; override;
+    public
+        constructor Create(const Iterator: IMapIterator; FilterFunc: TCollectionFilterFunc; AllowRemoval: Boolean = true); virtual;
+        destructor Destroy; override;
+        function CurrentKey: ICollectable; override;
+    end;
+
+
+    ECollectionError = class(Exception)
+    private
+        FCollection: ICollection;
+        FErrorType: TCollectionError;
+    public
+        constructor Create(const Msg: String; const Collection: ICollection; ErrorType: TCollectionError);
+        property Collection: ICollection read FCollection;
+        property ErrorType: TCollectionError read FErrorType;
+    end;
+
+implementation
+
+uses
+    Math,
+    CollArray, CollHash, CollList, CollPArray, CollWrappers;
+
+var
+    FDefaultComparator: IComparator;
+    FNaturalComparator: IComparator;
+    FReverseNaturalComparator: IComparator;
+
+{ TCollectionPosition }
+constructor TCollectionPosition.Create(Found: Boolean);
+begin
+    FFound := Found;
+end;
+
+{ TAbstractComparator }
+class function TAbstractComparator.GetDefaultComparator: IComparator;
+begin
+    if FDefaultComparator = nil then
+        FDefaultComparator := TDefaultComparator.Create;
+    Result := FDefaultComparator;
+end;
+
+class function TAbstractComparator.GetNaturalComparator: IComparator;
+begin
+    if FNaturalComparator = nil then
+        FNaturalComparator := TNaturalComparator.Create;
+    Result := FNaturalComparator;
+end;
+
+class function TAbstractComparator.GetReverseNaturalComparator: IComparator;
+begin
+    if FReverseNaturalComparator = nil then
+        FReverseNaturalComparator := TReverseNaturalComparator.Create;
+    Result := FReverseNaturalComparator;
+end;
+
+function TAbstractComparator.GetInstance: TObject;
+begin
+    Result := Self;
+end;
+
+function TAbstractComparator.Equals(const Comparator: IComparator): Boolean;
+begin
+    Result := (Self = Comparator.GetInstance); 
+end;
+
+{ TDefaultComparator }
+constructor TDefaultComparator.Create;
+begin
+    // Empty
+end;
+
+function TDefaultComparator.Compare(const Item1, Item2: ICollectable): Integer;
+var
+    Value1, Value2: Integer;
+begin
+    if Item1 <> nil then
+        Value1 := Integer(Pointer(Item1))
+    else
+        Value1 := Low(Integer);
+    if Item2 <> nil then
+        Value2 := Integer(Pointer(Item2))
+    else
+        Value2 := Low(Integer);
+    if (Value1 < Value2) then
+        Result := -1
+    else if (Value1 > Value2) then
+        Result := 1
+    else
+        Result := 0;
+end;
+
+function TDefaultComparator.Equals(const Item1, Item2: ICollectable): Boolean;
+begin
+    Result := (Item1 = Item2);
+end;
+
+{ TNaturalComparator }
+constructor TNaturalComparator.Create;
+begin
+    // Empty
+end;
+
+function TNaturalComparator.Compare(const Item1, Item2: ICollectable): Integer;
+begin
+    if (Item1 = nil) and (Item2 <> nil) then
+        Result := -1
+    else if (Item1 <> nil) and (Item2 = nil) then
+        Result := 1
+    else if (Item1 = nil) and (Item2 = nil) then
+        Result := 0
+    else
+        Result := (Item1 as IComparable).CompareTo(Item2);
+end;
+
+function TNaturalComparator.Equals(const Item1, Item2: ICollectable): Boolean;
+begin
+    if (Item1 = nil) or (Item2 = nil) then
+        Result := (Item1 = Item2)
+    else
+    begin
+        Result := (Item1 as IEquatable).Equals(Item2);
+    end;
+end;
+
+{ TReverseNaturalComparator }
+constructor TReverseNaturalComparator.Create;
+begin
+    // Empty
+end;
+
+function TReverseNaturalComparator.Compare(const Item1, Item2: ICollectable): Integer;
+begin
+    if (Item1 = nil) and (Item2 <> nil) then
+        Result := 1
+    else if (Item1 <> nil) and (Item2 = nil) then
+        Result := -1
+    else if (Item1 = nil) and (Item2 = nil) then
+        Result := 0
+    else
+        Result := -(Item1 as IComparable).CompareTo(Item2);
+end;
+
+function TReverseNaturalComparator.Equals(const Item1, Item2: ICollectable): Boolean;
+begin
+    if (Item1 = nil) or (Item2 = nil) then
+        Result := (Item1 = Item2)
+    else
+        Result := (Item1 as IEquatable).Equals(Item2);
+end;
+
+{ TAssociation }
+constructor TAssociation.Create(const Key, Value: ICollectable);
+begin
+    FKey := Key;
+    FValue := Value;
+end;
+
+destructor TAssociation.Destroy;
+begin
+    FKey := nil;
+    FValue := nil;
+    inherited Destroy;
+end;
+
+function TAssociation.GetInstance: TObject;
+begin
+    Result := Self;
+end;
+
+function TAssociation.GetKey: ICollectable;
+begin
+    Result := FKey;
+end;
+
+function TAssociation.GetValue: ICollectable;
+begin
+    Result := FValue;
+end;
+
+
+{ TIntegerAssociation }
+constructor TIntegerAssociation.Create(const Key: Integer; const Value: ICollectable);
+begin
+    FKey := Key;
+    FValue := Value;
+end;
+
+destructor TIntegerAssociation.Destroy;
+begin
+    FValue := nil;
+    inherited Destroy;
+end;
+
+function TIntegerAssociation.GetInstance: TObject;
+begin
+    Result := Self;
+end;
+
+function TIntegerAssociation.GetKey: Integer;
+begin
+    Result := FKey;
+end;
+
+function TIntegerAssociation.GetValue: ICollectable;
+begin
+    Result := FValue;
+end;
+
+
+{ TStringAssociation }
+constructor TStringAssociation.Create(const Key: String; const Value: ICollectable);
+begin
+    FKey := Key;
+    FValue := Value;
+end;
+
+destructor TStringAssociation.Destroy;
+begin
+    FValue := nil;
+    inherited Destroy;
+end;
+
+function TStringAssociation.GetInstance: TObject;
+begin
+    Result := Self;
+end;
+
+function TStringAssociation.GetKey: String;
+begin
+    Result := FKey;
+end;
+
+function TStringAssociation.GetValue: ICollectable;
+begin
+    Result := FValue;
+end;
+
+
+{ TAbstractIterator }
+constructor TAbstractIterator.Create(AllowRemoval: Boolean);
+begin
+    inherited Create;
+    FAllowRemoval := AllowRemoval;
+    FEOF := true;
+    FItem := nil;
+end;
+
+procedure TAbstractIterator.AfterConstruction;
+begin
+    inherited AfterConstruction;
+    First;
+end;
+
+function TAbstractIterator.GetAllowRemoval: Boolean;
+begin
+    Result := FAllowRemoval;
+end;
+
+function TAbstractIterator.CurrentItem: ICollectable;
+begin
+    Result := FItem;
+end;
+
+function TAbstractIterator.EOF: Boolean;
+begin
+    Result := FEOF;
+end;
+
+function TAbstractIterator.First: ICollectable;
+begin
+    FEOF := false;
+    FItem := TrueFirst;
+    if FItem = nil then
+        FEOF := true;
+    Result := FItem;
+end;
+
+function TAbstractIterator.Next: ICollectable;
+begin
+    if not FEOF then
+    begin
+        FItem := TrueNext;
+        if FItem = nil then
+            FEOF := true;
+    end;
+    Result := FItem;
+end;
+
+function TAbstractIterator.Remove: Boolean;
+begin
+    if (FItem <> nil) and FAllowRemoval then
+    begin
+        TrueRemove;
+        FItem := nil;
+        Result := true;
+    end
+    else
+        Result := false;
+end;
+
+{ TAbstractAssociationIterator }
+constructor TAbstractAssociationIterator.Create(AllowRemoval: Boolean);
+begin
+    inherited Create;
+    FAllowRemoval := AllowRemoval;
+    FEOF := true;
+    FAssociation := nil;
+end;
+
+procedure TAbstractAssociationIterator.AfterConstruction;
+begin
+    inherited AfterConstruction;
+    First;
+end;
+
+function TAbstractAssociationIterator.GetAllowRemoval: Boolean;
+begin
+    Result := FAllowRemoval;
+end;
+
+function TAbstractAssociationIterator.CurrentKey: ICollectable;
+begin
+    if FAssociation <> nil then
+        Result := FAssociation.GetKey
+    else
+        Result := nil;
+end;
+
+function TAbstractAssociationIterator.CurrentItem: ICollectable;
+begin
+    if FAssociation <> nil then
+        Result := FAssociation.GetValue
+    else
+        Result := nil;
+end;
+
+function TAbstractAssociationIterator.EOF: Boolean;
+begin
+    Result := FEOF;
+end;
+
+function TAbstractAssociationIterator.First: ICollectable;
+begin
+    FAssociation := TrueFirst;
+    if FAssociation <> nil then
+    begin
+        Result := FAssociation.GetValue;
+        FEOF := false;
+    end
+    else
+    begin
+        Result := nil;
+        FEOF := true;
+    end;
+end;
+
+function TAbstractAssociationIterator.Next: ICollectable;
+begin
+    if not FEOF then
+    begin
+        FAssociation := TrueNext;
+        if FAssociation <> nil then
+            Result := FAssociation.GetValue
+        else
+        begin
+            Result := nil;
+            FEOF := true;
+        end;
+    end;
+end;
+
+function TAbstractAssociationIterator.Remove: Boolean;
+begin
+    if (FAssociation <> nil) and FAllowRemoval then
+    begin
+        TrueRemove;
+        FAssociation := nil;
+        Result := true;
+    end
+    else
+        Result := false;
+end;
+
+{ TAbstractIntegerAssociationIterator }
+constructor TAbstractIntegerAssociationIterator.Create(AllowRemoval: Boolean);
+begin
+    inherited Create;
+    FAllowRemoval := AllowRemoval;
+    FEOF := true;
+    FAssociation := nil;
+end;
+
+procedure TAbstractIntegerAssociationIterator.AfterConstruction;
+begin
+    inherited AfterConstruction;
+    First;
+end;
+
+function TAbstractIntegerAssociationIterator.GetAllowRemoval: Boolean;
+begin
+    Result := FAllowRemoval;
+end;
+
+function TAbstractIntegerAssociationIterator.CurrentKey: Integer;
+begin
+    if FAssociation <> nil then
+        Result := FAssociation.GetKey
+    else
+        Result := 0;
+end;
+
+function TAbstractIntegerAssociationIterator.CurrentItem: ICollectable;
+begin
+    if FAssociation <> nil then
+        Result := FAssociation.GetValue
+    else
+        Result := nil;
+end;
+
+function TAbstractIntegerAssociationIterator.EOF: Boolean;
+begin
+    Result := FEOF;
+end;
+
+function TAbstractIntegerAssociationIterator.First: ICollectable;
+begin
+    FAssociation := TrueFirst;
+    if FAssociation <> nil then
+    begin
+        Result := FAssociation.GetValue;
+        FEOF := false;
+    end
+    else
+    begin
+        Result := nil;
+        FEOF := true;
+    end;
+end;
+
+function TAbstractIntegerAssociationIterator.Next: ICollectable;
+begin
+    if not FEOF then
+    begin
+        FAssociation := TrueNext;
+        if FAssociation <> nil then
+            Result := FAssociation.GetValue
+        else
+        begin
+            Result := nil;
+            FEOF := true;
+        end;
+    end;
+end;
+
+function TAbstractIntegerAssociationIterator.Remove: Boolean;
+begin
+    if (FAssociation <> nil) and FAllowRemoval then
+    begin
+        TrueRemove;
+        FAssociation := nil;
+        Result := true;
+    end
+    else
+        Result := false;
+end;
+
+{ TAbstractStringAssociationIterator }
+constructor TAbstractStringAssociationIterator.Create(AllowRemoval: Boolean);
+begin
+    inherited Create;
+    FAllowRemoval := AllowRemoval;
+    FEOF := true;
+    FAssociation := nil;
+end;
+
+procedure TAbstractStringAssociationIterator.AfterConstruction;
+begin
+    inherited AfterConstruction;
+    First;
+end;
+
+function TAbstractStringAssociationIterator.GetAllowRemoval: Boolean;
+begin
+    Result := FAllowRemoval;
+end;
+
+function TAbstractStringAssociationIterator.CurrentKey: String;
+begin
+    if FAssociation <> nil then
+        Result := FAssociation.GetKey
+    else
+        Result := '';
+end;
+
+function TAbstractStringAssociationIterator.CurrentItem: ICollectable;
+begin
+    if FAssociation <> nil then
+        Result := FAssociation.GetValue
+    else
+        Result := nil;
+end;
+
+function TAbstractStringAssociationIterator.EOF: Boolean;
+begin
+    Result := FEOF;
+end;
+
+function TAbstractStringAssociationIterator.First: ICollectable;
+begin
+    FAssociation := TrueFirst;
+    if FAssociation <> nil then
+    begin
+        Result := FAssociation.GetValue;
+        FEOF := false;
+    end
+    else
+    begin
+        Result := nil;
+        FEOF := true;
+    end;
+end;
+
+function TAbstractStringAssociationIterator.Next: ICollectable;
+begin
+    if not FEOF then
+    begin
+        FAssociation := TrueNext;
+        if FAssociation <> nil then
+            Result := FAssociation.GetValue
+        else
+        begin
+            Result := nil;
+            FEOF := true;
+        end;
+    end;
+end;
+
+function TAbstractStringAssociationIterator.Remove: Boolean;
+begin
+    if (FAssociation <> nil) and FAllowRemoval then
+    begin
+        TrueRemove;
+        FAssociation := nil;
+        Result := true;
+    end
+    else
+        Result := false;
+end;
+
+{ TAssociationIterator }
+constructor TAssociationIterator.Create(const Iterator: IIterator);
+begin
+    inherited Create(Iterator.GetAllowRemoval);
+    FIterator := Iterator;
+end;
+
+destructor TAssociationIterator.Destroy;
+begin
+    FIterator := nil;
+    inherited Destroy;
+end;
+
+function TAssociationIterator.TrueFirst: ICollectable;
+var
+    Association: IAssociation;
+begin
+    Association := FIterator.First as IAssociation;
+    if Association <> nil then
+        Result := Association.GetValue
+    else
+        Result := nil;
+end;
+
+function TAssociationIterator.TrueNext: ICollectable;
+var
+    Association: IAssociation;
+begin
+    Association := (FIterator.Next as IAssociation);
+    if Association <> nil then
+        Result := Association.GetValue
+    else
+        Result := nil;
+end;
+
+procedure TAssociationIterator.TrueRemove;
+begin
+    FIterator.Remove;
+end;
+
+function TAssociationIterator.CurrentItem: ICollectable;
+var
+    Association: IAssociation;
+begin
+    Association := FIterator.CurrentItem as IAssociation;
+    if Association <> nil then
+        Result := Association.GetValue
+    else
+        Result := nil;
+end;
+
+function TAssociationIterator.CurrentKey: ICollectable;
+var
+    Association: IAssociation;
+begin
+    Association := FIterator.CurrentItem  as IAssociation;
+    if Association <> nil then
+        Result := Association.GetKey
+    else
+        Result := nil;
+end;
+
+{ TAssociationComparator }
+constructor TAssociationComparator.Create(NaturalKeys: Boolean);
+begin
+    inherited Create;
+    if NaturalKeys then
+        FKeyComparator := TAbstractComparator.GetNaturalComparator
+    else
+        FKeyComparator := TAbstractComparator.GetDefaultComparator;
+end;
+
+destructor TAssociationComparator.Destroy;
+begin
+    FKeyComparator := nil;
+    inherited Destroy;
+end;
+
+function TAssociationComparator.GetKeyComparator: IComparator;
+begin
+    Result := FKeyComparator;
+end;
+
+procedure TAssociationComparator.SetKeyComparator(Value: IComparator);
+begin
+    FKeyComparator := Value;
+end;
+
+function TAssociationComparator.Compare(const Item1, Item2: ICollectable): Integer;
+begin
+    Result := KeyComparator.Compare((Item1 as IAssociation).GetKey, (Item2 as IAssociation).GetKey);
+end;
+
+function TAssociationComparator.Equals(const Item1, Item2: ICollectable): Boolean;
+begin
+    Result := KeyComparator.Equals((Item1 as IAssociation).GetKey, (Item2 as IAssociation).GetKey);
+end;
+
+{ TIntegerAssociationComparator }
+constructor TIntegerAssociationComparator.Create;
+begin
+    inherited Create;
+end;
+
+destructor TIntegerAssociationComparator.Destroy;
+begin
+    inherited Destroy;
+end;
+
+function TIntegerAssociationComparator.Compare(const Item1, Item2: ICollectable): Integer;
+var
+    Key1, Key2: Integer;
+begin
+    Key1 := (Item1 as IIntegerAssociation).GetKey;
+    Key2 := (Item2 as IIntegerAssociation).GetKey;
+    if Key1 < Key2 then
+        Result := -1
+    else if Key1 > Key2 then
+        Result := 1
+    else
+        Result := 0;
+end;
+
+function TIntegerAssociationComparator.Equals(const Item1, Item2: ICollectable): Boolean;
+begin
+    Result := ((Item1 as IIntegerAssociation).GetKey = (Item2 as IIntegerAssociation).GetKey);
+end;
+
+{ TStringAssociationComparator }
+constructor TStringAssociationComparator.Create;
+begin
+    inherited Create;
+end;
+
+destructor TStringAssociationComparator.Destroy;
+begin
+    inherited Destroy;
+end;
+
+function TStringAssociationComparator.Compare(const Item1, Item2: ICollectable): Integer;
+var
+    Key1, Key2: String;
+begin
+    Key1 := (Item1 as IStringAssociation).GetKey;
+    Key2 := (Item2 as IStringAssociation).GetKey;
+    if Key1 < Key2 then
+        Result := -1
+    else if Key1 > Key2 then
+        Result := 1
+    else
+        Result := 0;
+end;
+
+function TStringAssociationComparator.Equals(const Item1, Item2: ICollectable): Boolean;
+begin
+    Result := ((Item1 as IStringAssociation).GetKey = (Item2 as IStringAssociation).GetKey);
+end;
+
+{ TAssociationKeyIterator }
+constructor TAssociationKeyIterator.Create(const Iterator: IMapIterator);
+begin
+    inherited Create(Iterator.GetAllowRemoval);
+    FIterator := Iterator;
+end;
+
+destructor TAssociationKeyIterator.Destroy;
+begin
+    FIterator := nil;
+    inherited Destroy;
+end;
+
+function TAssociationKeyIterator.TrueFirst: ICollectable;
+begin
+    FIterator.First;
+    Result := FIterator.CurrentKey;
+end;
+
+function TAssociationKeyIterator.TrueNext: ICollectable;
+begin
+    FIterator.Next;
+    Result := FIterator.CurrentKey;
+end;
+
+procedure TAssociationKeyIterator.TrueRemove;
+begin
+    FIterator.Remove;
+end;
+
+{ TFilterIterator }
+constructor TFilterIterator.Create(const Iterator: IIterator; const Filter: IFilter; AllowRemoval: Boolean = true);
+begin
+    FIterator := Iterator;
+    FFilter := Filter;
+end;
+
+destructor TFilterIterator.Destroy;
+begin
+    FIterator := nil;
+    FFilter := nil;
+end;
+
+function TFilterIterator.TrueFirst: ICollectable;
+var
+    Item: ICollectable;
+begin
+    Item := FIterator.First;
+    while not FIterator.EOF do
+    begin
+        if FFilter.Accept(Item) then
+            break
+        else
+            Item := FIterator.Next;
+    end;
+    Result := Item;
+end;
+
+function TFilterIterator.TrueNext: ICollectable;
+var
+    Item: ICollectable;
+begin
+    Item := FIterator.Next;
+    while not FIterator.EOF do
+    begin
+        if FFilter.Accept(Item) then
+            break
+        else
+            Item := FIterator.Next;
+    end;
+    Result := Item;
+end;
+
+procedure TFilterIterator.TrueRemove;
+begin
+    FIterator.Remove;
+end;
+
+{ TFilterFuncIterator }
+constructor TFilterFuncIterator.Create(const Iterator: IIterator; FilterFunc: TCollectionFilterFunc; AllowRemoval: Boolean = true);
+begin
+    FIterator := Iterator;
+    FFilterFunc := FilterFunc;
+end;
+
+destructor TFilterFuncIterator.Destroy;
+begin
+    FIterator := nil;
+    FFilterFunc := nil;
+end;
+
+function TFilterFuncIterator.TrueFirst: ICollectable;
+var
+    Item: ICollectable;
+begin
+    Item := FIterator.First;
+    while not FIterator.EOF do
+    begin
+        if FFilterFunc(Item) then
+            break
+        else
+            Item := FIterator.Next;
+    end;
+    Result := Item;
+end;
+
+function TFilterFuncIterator.TrueNext: ICollectable;
+var
+    Item: ICollectable;
+begin
+    Item := FIterator.Next;
+    while not FIterator.EOF do
+    begin
+        if FFilterFunc(Item) then
+            break
+        else
+            Item := FIterator.Next;
+    end;
+    Result := Item;
+end;
+
+procedure TFilterFuncIterator.TrueRemove;
+begin
+    FIterator.Remove;
+end;
+
+{ TKeyFilterMapIterator }
+constructor TKeyFilterMapIterator.Create(const Iterator: IMapIterator; const Filter: IFilter; AllowRemoval: Boolean = true);
+begin
+    FIterator := Iterator;
+    FFilter := Filter;
+end;
+
+destructor TKeyFilterMapIterator.Destroy;
+begin
+    FIterator := nil;
+    FFilter := nil;
+end;
+
+function TKeyFilterMapIterator.TrueFirst: ICollectable;
+var
+    Key, Item: ICollectable;
+begin
+    Item := FIterator.First;
+    while not FIterator.EOF do
+    begin
+        Key := FIterator.CurrentKey;
+        if FFilter.Accept(Key) then
+            break
+        else
+            Item := FIterator.Next;
+    end;
+    Result := Item;
+end;
+
+function TKeyFilterMapIterator.TrueNext: ICollectable;
+var
+    Key, Item: ICollectable;
+begin
+    Item := FIterator.Next;
+    while not FIterator.EOF do
+    begin
+        Key := FIterator.CurrentKey;
+        if FFilter.Accept(Key) then
+            break
+        else
+            Item := FIterator.Next;
+    end;
+    Result := Item;
+end;
+
+procedure TKeyFilterMapIterator.TrueRemove;
+begin
+    FIterator.Remove;
+end;
+
+function TKeyFilterMapIterator.CurrentKey: ICollectable;
+begin
+    Result := FIterator.CurrentKey;
+end;
+
+{ TKeyFilterFuncMapIterator }
+constructor TKeyFilterFuncMapIterator.Create(const Iterator: IMapIterator; FilterFunc: TCollectionFilterFunc; AllowRemoval: Boolean = true);
+begin
+    FIterator := Iterator;
+    FFilterFunc := FilterFunc;
+end;
+
+destructor TKeyFilterFuncMapIterator.Destroy;
+begin
+    FIterator := nil;
+    FFilterFunc := nil;
+end;
+
+function TKeyFilterFuncMapIterator.TrueFirst: ICollectable;
+var
+    Key, Item: ICollectable;
+begin
+    Item := FIterator.First;
+    while not FIterator.EOF do
+    begin
+        Key := FIterator.CurrentKey;
+        if FFilterFunc(Key) then
+            break
+        else
+            Item := FIterator.Next;
+    end;
+    Result := Item;
+end;
+
+function TKeyFilterFuncMapIterator.TrueNext: ICollectable;
+var
+    Key, Item: ICollectable;
+begin
+    Item := FIterator.Next;
+    while not FIterator.EOF do
+    begin
+        Key := FIterator.CurrentKey;
+        if FFilterFunc(Key) then
+            break
+        else
+            Item := FIterator.Next;
+    end;
+    Result := Item;
+end;
+
+procedure TKeyFilterFuncMapIterator.TrueRemove;
+begin
+    FIterator.Remove;
+end;
+
+function TKeyFilterFuncMapIterator.CurrentKey: ICollectable;
+begin
+    Result := FIterator.CurrentKey;
+end;
+
+
+{ TAbstractCollection }
+constructor TAbstractCollection.Create;
+begin
+    Create(false);
+end;
+
+constructor TAbstractCollection.Create(NaturalItemsOnly: Boolean);
+begin
+    FCreated := false;
+    inherited Create;
+    FNaturalItemsOnly := NaturalItemsOnly or GetAlwaysNaturalItems;
+    if FNaturalItemsOnly then
+        FComparator := TAbstractComparator.GetNaturalComparator
+    else
+        FComparator := TAbstractComparator.GetDefaultComparator;
+    FIgnoreErrors := [ceDuplicate];
+end;
+
+constructor TAbstractCollection.Create(const ItemArray: array of ICollectable);
+begin
+    Create(ItemArray, false);
+end;
+
+// Fixed size collections must override this.
+constructor TAbstractCollection.Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean);
+var
+    I: Integer;
+begin
+    Create(NaturalItemsOnly);
+    if not FixedSize then
+    begin
+        Capacity := Length(ItemArray);
+        for I := Low(ItemArray) to High(ItemArray) do
+        begin
+            Add(ItemArray[I]);
+        end;
+    end;
+end;
+
+// Fixed size collections must override this.
+constructor TAbstractCollection.Create(const Collection: ICollection);
+var
+    Iterator: IIterator;
+begin
+    Create(Collection.GetNaturalItemsOnly);
+    InitFrom(Collection);
+    if not FixedSize then
+    begin
+        Capacity := Collection.GetSize;
+        Iterator := Collection.GetIterator;
+        while not Iterator.EOF do
+        begin
+            Add(Iterator.CurrentItem);
+            Iterator.Next;
+        end;
+    end;
+end;
+
+destructor TAbstractCollection.Destroy;
+begin
+    FCreated := false;
+    FComparator := nil;
+    inherited Destroy;
+end;
+
+procedure TAbstractCollection.CollectionError(ErrorType: TCollectionError);
+var
+    Msg: String;
+begin
+    if not (ErrorType in FIgnoreErrors) then
+    begin
+        case ErrorType of
+        ceDuplicate: Msg := 'Collection does not allow duplicates.';
+        ceDuplicateKey: Msg := 'Collection does not allow duplicate keys.';
+        ceFixedSize: Msg := 'Collection has fixed size.';
+        ceNilNotAllowed: Msg := 'Collection does not allow nil.';
+        ceNotNaturalItem: Msg := 'Collection only accepts natural items.';
+        ceOutOfRange: Msg := 'Index out of collection range.';
+        end;
+        // If exception is thrown during construction, collection cannot be
+        // passed to it as destructor is automatically called and this leaves an
+        // interface reference to a destroyed object and crashes.
+        if FCreated then
+            raise ECollectionError.Create(Msg, Self, ErrorType)
+        else
+            raise ECollectionError.Create(Msg, nil, ErrorType);
+    end;
+end;
+
+procedure TAbstractCollection.InitFrom(const Collection: ICollection);
+begin
+    Comparator := Collection.GetComparator;
+    IgnoreErrors := Collection.GetIgnoreErrors;
+end;
+
+// Implementations should override this if possible
+function TAbstractCollection.TrueItemCount(const Item: ICollectable): Integer;
+var
+    Iterator: IIterator;
+    Total: Integer;
+begin
+    Total := 0;
+    Iterator := GetIterator;
+    while not Iterator.EOF do
+    begin
+        if FComparator.Equals(Item, Iterator.CurrentItem) then
+            Inc(Total);
+        Iterator.Next;
+    end;
+    Result := Total;
+end;
+
+class function TAbstractCollection.GetAlwaysNaturalItems: Boolean;
+begin
+    Result := false;
+end;
+
+function TAbstractCollection.GetAsArray: TCollectableArray;
+var
+    Iterator: IIterator;
+    Working: TCollectableArray;
+    I: Integer;
+begin
+    SetLength(Working, Size);
+    I := 0;
+    Iterator := GetIterator;
+    while not Iterator.EOF do
+    begin
+        Working[I] := Iterator.CurrentItem;
+        Inc(I);
+        Iterator.Next;
+    end;
+    Result := Working;
+end;
+
+function TAbstractCollection.GetComparator: IComparator;
+begin
+    Result := FComparator;
+end;
+
+function TAbstractCollection.GetDuplicates: Boolean;
+begin
+    Result := true; // Sets and lists override this.
+end;
+
+procedure TAbstractCollection.SetComparator(const Value: IComparator);
+begin
+    if Value = nil then
+    begin
+        if NaturalItemsOnly then
+            FComparator := TAbstractComparator.GetNaturalComparator
+        else
+            FComparator := TAbstractComparator.GetDefaultComparator;
+    end
+    else
+        FComparator := Value;
+end;
+
+function TAbstractCollection.GetFixedSize: Boolean;
+begin
+    Result := false;
+end;
+
+function TAbstractCollection.GetIgnoreErrors: TCollectionErrors;
+begin
+    Result := FIgnoreErrors;
+end;
+
+procedure TAbstractCollection.SetIgnoreErrors(Value: TCollectionErrors);
+begin
+    FIgnoreErrors := Value;
+end;
+
+function TAbstractCollection.GetInstance: TObject;
+begin
+    Result := Self;
+end;
+
+function TAbstractCollection.GetIterator(const Filter: IFilter): IIterator;
+var
+    Iterator: IIterator;
+begin
+    Iterator := GetIterator;
+    Result := TFilterIterator.Create(Iterator, Filter, Iterator.GetAllowRemoval);
+end;
+
+function TAbstractCollection.GetIterator(FilterFunc: TCollectionFilterFunc): IIterator;
+var
+    Iterator: IIterator;
+begin
+    Iterator := GetIterator;
+    Result := TFilterFuncIterator.Create(Iterator, FilterFunc, Iterator.GetAllowRemoval);
+end;
+
+function TAbstractCollection.GetNaturalItemsOnly: Boolean;
+begin
+    Result := FNaturalItemsOnly;
+end;
+
+function TAbstractCollection.Add(const Item: ICollectable): Boolean;
+var
+    ItemError: TCollectionError;
+    Success: Boolean;
+begin
+    ItemError := ItemAllowed(Item); // Can be natural items only error or nil not allowed error
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Success := false;
+    end
+    else if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+        Success := false;
+    end
+    else
+    begin
+        Success := TrueAdd(Item);
+    end;
+    Result := Success;
+end;
+
+function TAbstractCollection.Add(const ItemArray: array of ICollectable): Integer;
+var
+    Item: ICollectable;
+    ItemError: TCollectionError;
+    I, Count: Integer;
+    Success: Boolean;
+begin
+    Count := 0;
+    if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+    end
+    else
+    begin
+        for I := Low(ItemArray) to High(ItemArray) do
+        begin
+            Item := ItemArray[I];
+            ItemError := ItemAllowed(Item);
+            if ItemError <> ceOK then
+            begin
+                CollectionError(ItemError);
+                Success := false;
+            end
+            else
+            begin
+                Success := TrueAdd(Item);
+            end;
+            if Success then
+                Inc(Count);
+        end;
+    end;
+    Result := Count;
+end;
+
+function TAbstractCollection.Add(const Collection: ICollection): Integer;
+var
+    Iterator: IIterator;
+    Item: ICollectable;
+    ItemError: TCollectionError;
+    Count: Integer;
+    Success: Boolean;
+begin
+    Count := 0;
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Item := Iterator.CurrentItem;
+        ItemError := ItemAllowed(Item);
+        if ItemError <> ceOK then
+        begin
+            CollectionError(ItemError);
+            Success := false;
+        end
+        else if FixedSize then
+        begin
+            CollectionError(ceFixedSize);
+            Success := false;
+        end
+        else
+        begin
+            Success := TrueAdd(Item);
+        end;
+        if Success then
+            Inc(Count);
+        Iterator.Next;
+    end;
+    Result := Count;
+end;
+
+procedure TAbstractCollection.AfterConstruction;
+begin
+    inherited AfterConstruction;
+    FCreated := true;
+end;
+
+procedure TAbstractCollection.BeforeDestruction;
+begin
+    if not FixedSize then
+        TrueClear;
+    inherited BeforeDestruction;
+end;
+
+function TAbstractCollection.Clear: Integer;
+begin
+    if not FixedSize then
+    begin
+        Result := Size;
+        TrueClear;
+    end
+    else
+    begin
+        CollectionError(ceFixedSize);
+        Result := 0;
+    end;
+end;
+
+function TAbstractCollection.Clone: ICollection;
+begin
+    Result := (TAbstractCollectionClass(ClassType)).Create(Self);
+end;
+
+function TAbstractCollection.Contains(const Item: ICollectable): Boolean;
+var
+    ItemError: TCollectionError;
+    Success: Boolean;
+begin
+    ItemError := ItemAllowed(Item);
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Success := false;
+    end
+    else
+    begin
+        Success := TrueContains(Item);
+    end;
+    Result := Success;
+end;
+
+function TAbstractCollection.Contains(const ItemArray: array of ICollectable): Boolean;
+var
+    I: Integer;
+    Success: Boolean;
+begin
+    Success := true;
+    for I := Low(ItemArray) to High(ItemArray) do
+    begin
+        Success := Success and Contains(ItemArray[I]);
+        if not Success then
+            break;
+    end;
+    Result := Success;
+end;
+
+function TAbstractCollection.Contains(const Collection: ICollection): Boolean;
+var
+    Iterator: IIterator;
+    Success: Boolean;
+begin
+    Success := true;
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Success := Success and Contains(Iterator.CurrentItem);
+        if not Success then
+            break;
+        Iterator.Next;
+    end;
+    Result := Success;
+end;
+
+function TAbstractCollection.Equals(const Collection: ICollection): Boolean;
+var
+    Iterator: IIterator;
+    Success: Boolean;
+begin
+    if Collection.GetType <> GetType then
+        Result := false
+    else if Collection.Size <> Size then
+        Result := false
+    else if not Collection.Comparator.Equals(Comparator) then
+        Result := false
+    else if not Collection.GetDuplicates and not GetDuplicates then
+    begin
+        // Not equal if any item not found in parameter collection
+        Success := true;
+        Iterator := GetIterator;
+        while not Iterator.EOF and Success do
+        begin
+            Success := Collection.Contains(Iterator.CurrentItem);
+            Iterator.Next;
+        end;
+        Result := Success;
+    end
+    else
+    begin
+        // Not equal if any item count not equal to item count in parameter collection
+        Success := true;
+        Iterator := GetIterator;
+        while not Iterator.EOF and Success do
+        begin
+            Success := (ItemCount(Iterator.CurrentItem) = Collection.ItemCount(Iterator.CurrentItem));
+            Iterator.Next;
+        end;
+        Result := Success;
+    end;
+end;
+
+function TAbstractCollection.Find(const Filter: IFilter): ICollectable;
+begin
+    Result := GetIterator(Filter).First;
+end;
+
+function TAbstractCollection.Find(FilterFunc: TCollectionFilterFunc): ICollectable;
+begin
+    Result := GetIterator(FilterFunc).First;
+end;
+
+function TAbstractCollection.FindAll(const Filter: IFilter): ICollection;
+var
+    ResultCollection: ICollection;
+    Iterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Self.GetIterator(Filter);
+    while not Iterator.EOF do
+    begin
+        ResultCollection.Add(Iterator.CurrentItem);
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.FindAll(FilterFunc: TCollectionFilterFunc): ICollection;
+var
+    ResultCollection: ICollection;
+    Iterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Self.GetIterator(FilterFunc);
+    while not Iterator.EOF do
+    begin
+        ResultCollection.Add(Iterator.CurrentItem);
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.IsEmpty: Boolean;
+begin
+    Result := (Size = 0);
+end;
+
+function TAbstractCollection.IsNaturalItem(const Item: ICollectable): Boolean;
+var
+    Temp: IUnknown;
+begin
+    if Item <> nil then
+        Result := (Item.QueryInterface(NaturalItemIID, Temp) <> E_NOINTERFACE)
+    else
+        Result := false;
+end;
+
+function TAbstractCollection.ItemAllowed(const Item: ICollectable): TCollectionError;
+begin
+    if NaturalItemsOnly and not IsNaturalItem(Item) then
+        Result := ceNotNaturalItem
+    else if not IsNilAllowed and (Item = nil) then
+        Result := ceNilNotAllowed
+    else
+        Result := ceOK;
+end;
+
+function TAbstractCollection.ItemCount(const Item: ICollectable): Integer;
+var
+    ItemError: TCollectionError;
+begin
+    ItemError := ItemAllowed(Item);
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Result := 0;
+    end
+    else if GetDuplicates then
+    begin
+        Result := TrueItemCount(Item);
+    end
+    else
+    begin
+        // Where duplicates are not allowed, TrueContains will be faster than TrueItemCount.
+        if TrueContains(Item) then
+            Result := 1
+        else
+            Result := 0;
+    end;
+end;
+
+function TAbstractCollection.ItemCount(const ItemArray: array of ICollectable): Integer;
+var
+    I: Integer;
+    Total: Integer;
+begin
+    Total := 0;
+    for I := Low(ItemArray) to High(ItemArray) do
+    begin
+        Total := Total + ItemCount(ItemArray[I]);
+    end;
+    Result := Total;
+end;
+
+function TAbstractCollection.ItemCount(const Collection: ICollection): Integer;
+var
+    Iterator: IIterator;
+    Total: Integer;
+begin
+    Total := 0;
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Total := Total + ItemCount(Iterator.CurrentItem);
+        Iterator.Next;
+    end;
+    Result := Total;
+end;
+
+function TAbstractCollection.Matching(const ItemArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(ItemArray) to High(ItemArray) do
+    begin
+        if Contains(ItemArray[I]) then
+            ResultCollection.Add(ItemArray[I]);
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.Matching(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    Iterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        if Contains(Iterator.CurrentItem) then
+            ResultCollection.Add(Iterator.CurrentItem);
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.Remove(const Item: ICollectable): ICollectable;
+var
+    ItemError: TCollectionError;
+begin
+    ItemError := ItemAllowed(Item);
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Result := nil;
+    end
+    else if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+        Result := nil;
+    end
+    else
+    begin
+        Result := TrueRemove(Item);
+    end;
+end;
+
+function TAbstractCollection.Remove(const ItemArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(ItemArray) to High(ItemArray) do
+    begin
+        ResultCollection.Add(Remove(ItemArray[I]));
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.Remove(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    Iterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        ResultCollection.Add(Remove(Iterator.CurrentItem));
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.RemoveAll(const Item: ICollectable): ICollection;
+var
+    ItemError: TCollectionError;
+begin
+    ItemError := ItemAllowed(Item);
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Result := nil;
+    end
+    else if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+        Result := nil;
+    end
+    else
+    begin
+        Result := TrueRemoveAll(Item);
+    end;
+end;
+
+function TAbstractCollection.RemoveAll(const ItemArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(ItemArray) to High(ItemArray) do
+    begin
+        ResultCollection.Add(RemoveAll(ItemArray[I]));
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.RemoveAll(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    Iterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        ResultCollection.Add(RemoveAll(Iterator.CurrentItem));
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.Retain(const ItemArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    Iterator: IIterator;
+    Item: ICollectable;
+    I: Integer;
+    Found, Success: Boolean;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := GetIterator;
+    while not Iterator.EOF do
+    begin
+        // Converting the array to a map would be faster but I don't want to
+        // couple base class code to a complex collection.
+        Found := false;
+        for I := Low(ItemArray) to High(ItemArray) do
+        begin
+            Item := Iterator.CurrentItem;
+            Found := Comparator.Equals(Item, ItemArray[I]);
+            if Found then
+                break;
+        end;
+        if not Found then
+        begin
+            Success := Iterator.Remove;
+            if Success then
+                ResultCollection.Add(Item);
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractCollection.Retain(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    Iterator: IIterator;
+    Item: ICollectable;
+    Success: Boolean;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := GetIterator;
+    while not Iterator.EOF do
+    begin
+        Item := Iterator.CurrentItem;
+        if not Collection.Contains(Item) then
+        begin
+            Success := Iterator.Remove;
+            if Success then
+                ResultCollection.Add(Item);
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+{ TAbstractBag }
+function TAbstractBag.CloneAsBag: IBag;
+begin
+    Result := (TAbstractBagClass(ClassType)).Create(Self);
+end;
+
+function TAbstractBag.GetNaturalItemIID: TGUID;
+begin
+    Result := EquatableIID;
+end;
+
+function TAbstractBag.GetType: TCollectionType;
+begin
+    Result := ctBag;
+end;
+
+function TAbstractBag.IsNilAllowed: Boolean;
+begin
+    Result := true;
+end;
+
+{ TAbstractSet }
+function TAbstractSet.TrueAdd(const Item: ICollectable): Boolean;
+var
+    Position: TCollectionPosition;
+begin
+    // Adds if not already present otherwise fails
+    Position := GetPosition(Item);
+    try
+        if Position.Found then
+        begin
+            CollectionError(ceDuplicate);
+            Result := false;
+        end
+        else
+        begin
+            TrueAdd2(Position, Item);
+            Result := true;
+        end;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractSet.TrueContains(const Item: ICollectable): Boolean;
+var
+    Position: TCollectionPosition;
+begin
+    Position := GetPosition(Item);
+    try
+        Result := Position.Found;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractSet.TrueRemove(const Item: ICollectable): ICollectable;
+var
+    Position: TCollectionPosition;
+begin
+    Position := GetPosition(Item);
+    try
+        if Position.Found then
+        begin
+            Result := TrueGet(Position);
+            TrueRemove2(Position);
+        end
+        else
+            Result := nil;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractSet.TrueRemoveAll(const Item: ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    RemovedItem: ICollectable;
+begin
+    ResultCollection := TPArrayBag.Create;
+    RemovedItem := TrueRemove(Item);
+    if RemovedItem <> nil then
+        ResultCollection.Add(RemovedItem);
+    Result := ResultCollection;
+end;
+
+function TAbstractSet.GetDuplicates: Boolean;
+begin
+    Result := false;
+end;
+
+function TAbstractSet.GetNaturalItemIID: TGUID;
+begin
+    Result := EquatableIID;
+end;
+
+function TAbstractSet.GetType: TCollectionType;
+begin
+    Result := ctSet;
+end;
+
+function TAbstractSet.CloneAsSet: ISet;
+begin
+    Result := (TAbstractSetClass(ClassType)).Create(Self);
+end;
+
+function TAbstractSet.Complement(const Universe: ISet): ISet;
+var
+    ResultSet: ISet;
+    Iterator: IIterator;
+    Item: ICollectable;
+begin
+    // Return items in universe not found in self.
+    ResultSet := TAbstractSetClass(ClassType).Create(NaturalItemsOnly);
+    Iterator := Universe.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Item := Iterator.CurrentItem;
+        if not Contains(Item) then
+            ResultSet.Add(Item);
+        Iterator.Next;
+    end;
+    Result := ResultSet;
+end;
+
+function TAbstractSet.Intersect(const Set2: ISet): ISet;
+var
+    ResultSet: ISet;
+    Iterator: IIterator;
+    Item: ICollectable;
+begin
+    // Return items found in self and parameter.
+    ResultSet := TAbstractSetClass(ClassType).Create(NaturalItemsOnly);
+    Iterator := GetIterator;
+    while not Iterator.EOF do
+    begin
+        Item := Iterator.CurrentItem;
+        if Contains(Item) and Set2.Contains(Item) then
+            ResultSet.Add(Iterator.CurrentItem);
+        Iterator.Next;
+    end;
+    Result := ResultSet;
+end;
+
+function TAbstractSet.IsNilAllowed: Boolean;
+begin
+    Result := false;
+end;
+
+function TAbstractSet.Union(const Set2: ISet): ISet;
+var
+    ResultSet: ISet;
+    Iterator: IIterator;
+    Item: ICollectable;
+begin
+    // Return items found in self or parameter.
+    ResultSet := CloneAsSet;
+    Iterator := Set2.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Item := Iterator.CurrentItem;
+        if not Contains(Item) and Set2.Contains(Item) then
+            ResultSet.Add(Iterator.CurrentItem);
+        Iterator.Next;
+    end;
+    Result := ResultSet;
+end;
+
+{ TAbstractList }
+constructor TAbstractList.Create(NaturalItemsOnly: Boolean);
+begin
+    inherited Create(NaturalItemsOnly);
+    FDuplicates := true;
+    FSorted := false;
+end;
+
+procedure TAbstractList.InitFrom(const Collection: ICollection);
+var
+    List: IList;
+begin
+    inherited InitFrom(Collection);
+    if Collection.QueryInterface(IList, List) = S_OK then
+    begin
+        FDuplicates := List.GetDuplicates;
+        FSorted := List.GetSorted;
+    end;
+end;
+
+function TAbstractList.TrueAdd(const Item: ICollectable): Boolean;
+var
+    SearchResult: TSearchResult;
+begin
+    Result := True;
+    if Sorted then
+    begin
+        // Insert in appropriate place to maintain sort order, unless duplicate
+        // not allowed.
+        SearchResult := BinarySearch(Item);
+        case SearchResult.ResultType of
+        srBeforeIndex: TrueInsert(SearchResult.Index, Item);
+        srFoundAtIndex: begin
+            if Duplicates then
+                TrueInsert(SearchResult.Index, Item)
+            else
+            begin
+                CollectionError(ceDuplicate);
+                Result := false;
+            end;
+        end;
+        srAfterEnd: TrueAppend(Item);
+        end;
+    end
+    else
+    begin
+        // Add to end, unless duplicate not allowed.
+        if not Duplicates and (SequentialSearch(Item, Comparator).ResultType = srFoundAtIndex) then
+        begin
+            CollectionError(ceDuplicate);
+            Result := false;
+        end
+        else
+            TrueAppend(Item);
+    end;
+end;
+
+function TAbstractList.TrueContains(const Item: ICollectable): Boolean;
+begin
+    if Sorted then
+        Result := BinarySearch(Item).ResultType = srFoundAtIndex
+    else
+        Result := SequentialSearch(Item, Comparator).ResultType = srFoundAtIndex
+end;
+
+function TAbstractList.TrueItemCount(const Item: ICollectable): Integer;
+var
+    SearchResult: TSearchResult;
+    Count: Integer;
+begin
+    if Sorted then
+    begin
+        // If sorted, use binary search.
+        Count := 0;
+        SearchResult := BinarySearch(Item);
+        if SearchResult.ResultType = srFoundAtIndex then
+        begin
+            repeat
+                Inc(Count);
+            until not Comparator.Equals(Item, Items[SearchResult.Index]);
+        end;
+        Result := Count;
+    end
+    else
+        // Resort to sequential search for unsorted
+        Result := inherited TrueItemCount(Item);
+end;
+
+function TAbstractList.TrueRemove(const Item: ICollectable): ICollectable;
+var
+    SearchResult: TSearchResult;
+begin
+    Result := nil;
+    if Sorted then
+    begin
+        SearchResult := BinarySearch(Item);
+        if SearchResult.ResultType = srFoundAtIndex then
+        begin
+            Result := TrueDelete(SearchResult.Index);
+        end;
+    end
+    else
+    begin
+        SearchResult := SequentialSearch(Item);
+        if SearchResult.ResultType = srFoundAtIndex then
+            Result := TrueDelete(SearchResult.Index);
+    end;
+end;
+
+function TAbstractList.TrueRemoveAll(const Item: ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    SearchResult: TSearchResult;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create;
+    if Sorted then
+    begin
+        SearchResult := BinarySearch(Item);
+        if SearchResult.ResultType = srFoundAtIndex then
+        begin
+            repeat
+                ResultCollection.Add(TrueDelete(SearchResult.Index));
+            until not Comparator.Equals(Item, Items[SearchResult.Index]);
+        end;
+    end
+    else
+    begin
+        I := 0;
+        while I < Size do
+        begin
+            if Comparator.Equals(Item, Items[I]) then
+            begin
+                ResultCollection.Add(TrueDelete(I));
+            end
+            else
+                Inc(I);
+        end;
+    end;
+    Result := ResultCollection;
+end;
+
+procedure TAbstractList.QuickSort(Lo, Hi: Integer; const Comparator: IComparator);
+var
+    I, J, Mid: Integer;
+begin
+    repeat
+        I := Lo;
+        J := Hi;
+        Mid := (Lo + Hi) div 2;
+        repeat
+            while Comparator.Compare(Items[I], Items[Mid]) < 0 do
+                Inc(I);
+            while Comparator.Compare(Items[J], Items[Mid]) > 0 do
+                Dec(J);
+            if I <= J then
+            begin
+                Exchange(I, J);
+                if Mid = I then
+                    Mid := J
+                else if Mid = J then
+                    Mid := I;
+                Inc(I);
+                Dec(J);
+            end;
+        until I > J;
+        if Lo < J then
+            QuickSort(Lo, J, Comparator);
+        Lo := I;
+    until I >= Hi;
+end;
+
+procedure TAbstractList.QuickSort(Lo, Hi: Integer; CompareFunc: TCollectionCompareFunc);
+var
+    I, J, Mid: Integer;
+begin
+    repeat
+        I := Lo;
+        J := Hi;
+        Mid := (Lo + Hi) div 2;
+        repeat
+            while CompareFunc(Items[I], Items[Mid]) < 0 do
+                Inc(I);
+            while CompareFunc(Items[J], Items[Mid]) > 0 do
+                Dec(J);
+            if I <= J then
+            begin
+                Exchange(I, J);
+                if Mid = I then
+                    Mid := J
+                else if Mid = J then
+                    Mid := I;
+                Inc(I);
+                Dec(J);
+            end;
+        until I > J;
+        if Lo < J then
+            QuickSort(Lo, J, CompareFunc);
+        Lo := I;
+    until I >= Hi;
+end;
+
+function TAbstractList.GetDuplicates: Boolean;
+begin
+    Result := FDuplicates;
+end;
+
+procedure TAbstractList.SetDuplicates(Value: Boolean);
+var
+    Iterator: IIterator;
+    Failed: Boolean;
+begin
+    Failed := false;
+    // If trying to set no duplicates, check there are no existing duplicates.
+    if not Value then
+    begin
+        Iterator := GetIterator;
+        while not Iterator.EOF and not Failed do
+        begin
+            Failed := (ItemCount(Iterator.CurrentItem) > 1);
+            Iterator.Next;
+        end;
+        if Failed then
+            CollectionError(ceDuplicate);
+    end;
+    if not Failed then
+        FDuplicates := Value;
+end;
+
+function TAbstractList.GetItem(Index: Integer): ICollectable;
+begin
+    if (Index < 0) or (Index >= Size) then
+    begin
+        CollectionError(ceOutOfRange);
+        Result := nil;
+    end
+    else
+        Result := TrueGetItem(Index);
+end;
+
+procedure TAbstractList.SetItem(Index: Integer; const Item: ICollectable);
+var
+    SearchResult: TSearchResult;
+begin
+    if (Index < 0) or (Index >= Size) then
+    begin
+        CollectionError(ceOutOfRange)
+    end
+    else if not Duplicates then
+    begin
+        // Find any duplicates
+        if Sorted then
+        begin
+            SearchResult := BinarySearch(Item);
+            case SearchResult.ResultType of
+            srBeforeIndex, srAfterEnd: begin        // If item is not present
+                FSorted := false;
+                TrueSetItem(Index, Item);
+            end;
+            srFoundAtIndex: begin                   // If item is already present
+                CollectionError(ceDuplicate);
+            end;
+            end;
+        end
+        else
+        begin
+            // If item is already present
+            if SequentialSearch(Item, Comparator).ResultType = srFoundAtIndex then
+            begin
+                CollectionError(ceDuplicate);
+            end
+            else
+            begin
+                TrueSetItem(Index, Item);
+            end;
+        end;
+    end
+    else
+    begin
+        FSorted := false;
+        TrueSetItem(Index, Item);
+    end;
+end;
+
+function TAbstractList.GetIterator: IIterator;
+begin
+    Result := TAbstractListIterator.Create(Self);
+end;
+
+function TAbstractList.GetNaturalItemIID: TGUID;
+begin
+    Result := ComparableIID;
+end;
+
+function TAbstractList.GetSorted: Boolean;
+begin
+    Result := FSorted;
+end;
+
+procedure TAbstractList.SetSorted(Value: Boolean);
+begin
+    if Value then
+        Sort;
+end;
+
+function TAbstractList.GetType: TCollectionType;
+begin
+    Result := ctList;
+end;
+
+function TAbstractList.BinarySearch(const Item: ICollectable): TSearchResult;
+var
+    Lo, Hi, Mid: Integer;
+    CompareResult: Integer;
+    Success: Boolean;
+begin
+    if Size = 0 then
+    begin
+        Result.ResultType := srAfterEnd;
+        Exit;
+    end;
+    Lo := 0;
+    Hi := Size - 1;
+    Success := false;
+    repeat
+        Mid := (Lo + Hi) div 2;
+        CompareResult := Comparator.Compare(Item, Items[Mid]);
+        if CompareResult = 0 then
+            Success := true
+        else if CompareResult > 0 then
+            Lo := Mid + 1
+        else
+            Hi := Mid - 1;
+    until (Lo > Hi) or Success;
+    if Success then
+    begin
+        // Move index back if in cluster of duplicates
+        while (Mid > 0) and Comparator.Equals(Item, Items[Mid - 1]) do
+            Dec(Mid);
+        Result.ResultType := srFoundAtIndex;
+        Result.Index := Mid;
+    end
+    else if CompareResult < 0 then
+    begin
+        Result.ResultType := srBeforeIndex;
+        Result.Index := Mid;
+    end
+    else if Hi < Size - 1 then
+    begin
+        Result.ResultType := srBeforeIndex;
+        Result.Index := Mid + 1;
+    end
+    else
+        Result.ResultType := srAfterEnd;
+end;
+
+function TAbstractList.CloneAsList: IList;
+begin
+    Result := (TAbstractListClass(ClassType)).Create(Self);
+end;
+
+function TAbstractList.Delete(Index: Integer): ICollectable;
+begin
+    if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+        Result := nil;
+    end
+    else if (Index < 0) or (Index >= Size) then
+    begin
+        CollectionError(ceOutOfRange);
+        Result := nil;
+    end
+    else
+    begin
+        Result := TrueDelete(Index);
+    end;
+end;
+
+procedure TAbstractList.Exchange(Index1, Index2: Integer);
+var
+    Item: ICollectable;
+begin
+    if (Index1 < 0) or (Index1 >= Size) then
+        CollectionError(ceOutOfRange);
+    if (Index2 < 0) or (Index2 >= Size) then
+        CollectionError(ceOutOfRange);
+    FSorted := false;
+    Item := ICollectable(Items[Index1]);
+    Items[Index1] := Items[Index2];
+    Items[Index2] := Item;
+end;
+
+function TAbstractList.First: ICollectable;
+begin
+    if Size > 0 then
+        Result := Items[0]
+    else
+        Result := nil;
+end;
+
+function TAbstractList.IndexOf(const Item: ICollectable): Integer;
+var
+    SearchResult: TSearchResult;
+begin
+    if Sorted then
+        SearchResult := BinarySearch(Item)
+    else
+        SearchResult := SequentialSearch(Item, Comparator);
+    if SearchResult.ResultType = srFoundAtIndex then
+        Result := SearchResult.Index
+    else
+        Result := -1;
+end;
+
+function TAbstractList.Insert(Index: Integer; const Item: ICollectable): Boolean;
+var
+    ItemError: TCollectionError;
+begin
+    ItemError := ItemAllowed(Item);
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Result := false;
+    end
+    else if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+        Result := false;
+    end
+    else if (Index < 0) or (Index > Size) then
+    begin
+        CollectionError(ceOutOfRange);
+        Result := false;
+    end
+    else
+    begin
+        FSorted := false;
+        if Index = Size then
+            TrueAdd(Item)
+        else
+            TrueInsert(Index, Item);
+        Result := true;
+    end;
+end;
+
+function TAbstractList.Insert(Index: Integer; const ItemArray: array of ICollectable): Integer;
+var
+    Item: ICollectable;
+    ItemError: TCollectionError;
+    I, NewIndex, Count: Integer;
+    Success: Boolean;
+begin
+    Count := 0;
+    if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+    end
+    else if (Index < 0) or (Index > Size) then
+    begin
+        CollectionError(ceOutOfRange);
+    end
+    else
+    begin
+        // Insert entire array in place in correct order
+        NewIndex := Index;
+        for I := Low(ItemArray) to High(ItemArray) do
+        begin
+            Item := ItemArray[I];
+            ItemError := ItemAllowed(Item);
+            if ItemError <> ceOK then
+            begin
+                CollectionError(ItemError);
+            end
+            else
+            begin
+                Success := Insert(NewIndex, Item);
+                if Success then
+                begin
+                    Inc(NewIndex);
+                    Inc(Count);
+                end;
+            end;
+        end;
+    end;
+    Result := Count;
+end;
+
+function TAbstractList.Insert(Index: Integer; const Collection: ICollection): Integer;
+var
+    Iterator: IIterator;
+    Item: ICollectable;
+    ItemError: TCollectionError;
+    NewIndex, Count: Integer;
+    Success: Boolean;
+begin
+    Count := 0;
+    if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+    end
+    else if (Index < 0) or (Index > Size) then
+    begin
+        CollectionError(ceOutOfRange);
+    end
+    else
+    begin
+        // Insert entire collection in place in correct order
+        NewIndex := Index;
+        Iterator := Collection.GetIterator;
+        while not Iterator.EOF do
+        begin
+            Item := Iterator.CurrentItem;
+            ItemError := ItemAllowed(Item);
+            if ItemError <> ceOK then
+            begin
+                CollectionError(ItemError);
+            end
+            else
+            begin
+                Success := Insert(NewIndex, Item);
+                if Success then
+                begin
+                    Inc(NewIndex);
+                    Inc(Count);
+                end;
+            end;
+            Iterator.Next;
+        end;
+    end;
+    Result := Count;
+end;
+
+function TAbstractList.IsNilAllowed: Boolean;
+begin
+    Result := true;
+end;
+
+function TAbstractList.Last: ICollectable;
+begin
+    if Size > 0 then
+        Result := Items[Size - 1]
+    else
+        Result := nil;
+end;
+
+function TAbstractList.Search(const Item: ICollectable; const SearchComparator: IComparator = nil): TSearchResult;
+begin
+    if Sorted and (SearchComparator = nil) then
+        Result := BinarySearch(Item)
+    else
+        Result := SequentialSearch(Item, SearchComparator);
+end;
+
+function TAbstractList.SequentialSearch(const Item: ICollectable; const SearchComparator: IComparator): TSearchResult;
+var
+    WorkingComparator: IComparator;
+    I: Integer;
+    Success: Boolean;
+begin
+    if SearchComparator = nil then
+        WorkingComparator := Comparator
+    else
+        WorkingComparator := SearchComparator;
+    Result.ResultType := srNotFound;
+    I := 0;
+    Success := false;
+    while (I < Size) and not Success do
+    begin
+        if WorkingComparator.Equals(Item, Items[I]) then
+        begin
+            Result.ResultType := srFoundAtIndex;
+            Result.Index := I;
+            Success := true;
+        end
+        else
+            Inc(I);
+    end;
+end;
+
+procedure TAbstractList.Sort(const SortComparator: IComparator);
+begin
+    if SortComparator = nil then
+    begin
+        if Size > 0 then
+            QuickSort(0, Size - 1, Comparator);
+        FSorted := true;
+    end
+    else
+    begin
+        if Size > 0 then
+            QuickSort(0, Size - 1, SortComparator);
+        FSorted := false;
+    end;
+end;
+
+procedure TAbstractList.Sort(CompareFunc: TCollectionCompareFunc);
+begin
+    if Size > 0 then
+        QuickSort(0, Size - 1, CompareFunc);
+    FSorted := false;
+end;
+
+{ TAbstractMap }
+constructor TAbstractMap.Create;
+begin
+    Create(false, true);
+end;
+
+constructor TAbstractMap.Create(NaturalItemsOnly: Boolean);
+begin
+    Create(NaturalItemsOnly, true);
+end;
+
+constructor TAbstractMap.Create(NaturalItemsOnly: Boolean; NaturalKeysOnly: Boolean);
+begin
+    inherited Create(NaturalItemsOnly);
+    FNaturalKeysOnly := NaturalKeysOnly or GetAlwaysNaturalKeys;
+    FAssociationComparator := TAssociationComparator.Create(FNaturalKeysOnly);
+    if FNaturalKeysOnly then
+        FKeyComparator := TAbstractComparator.GetNaturalComparator
+    else
+        FKeyComparator := TAbstractComparator.GetDefaultComparator;
+end;
+
+constructor TAbstractMap.Create(const ItemArray: array of ICollectable);
+begin
+    Create(ItemArray, true, true);
+end;
+
+constructor TAbstractMap.Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean);
+begin
+    Create(ItemArray, true, true);
+end;
+
+constructor TAbstractMap.Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean; NaturalKeysOnly: Boolean);
+var
+    I: Integer;
+begin
+    Create(true, NaturalKeysOnly);
+    if not FixedSize then
+    begin
+        Capacity := Length(ItemArray);
+        for I := Low(ItemArray) to High(ItemArray) do
+        begin
+            Add(ItemArray[I]);
+        end;
+    end;
+end;
+
+constructor TAbstractMap.Create(const KeyArray, ItemArray: array of ICollectable);
+begin
+    Create(KeyArray, ItemArray, false, true);
+end;
+
+constructor TAbstractMap.Create(const KeyArray, ItemArray: array of ICollectable; NaturalItemsOnly: Boolean);
+begin
+    Create(KeyArray, ItemArray, NaturalItemsOnly, true);
+end;
+
+constructor TAbstractMap.Create(const KeyArray, ItemArray: array of ICollectable; NaturalItemsOnly: Boolean; NaturalKeysOnly: Boolean);
+var
+    I, Lo, Hi: Integer;
+begin
+    Create(NaturalItemsOnly, NaturalKeysOnly);
+    if not FixedSize then
+    begin
+        Capacity := Min(Length(KeyArray), Length(ItemArray));
+        Lo := Max(Low(KeyArray), Low(ItemArray));
+        Hi := Min(High(KeyArray), High(ItemArray));
+        for I := Lo to Hi do
+        begin
+            Put(KeyArray[I], ItemArray[I]);
+        end;
+    end;
+end;
+
+constructor TAbstractMap.Create(const Map: IMap);
+var
+    MapIterator: IMapIterator;
+begin
+    Create(Map.GetNaturalItemsOnly, Map.GetNaturalKeysOnly);
+    InitFrom(Map);
+    if not FixedSize then
+    begin
+        Capacity := Map.GetSize;
+        MapIterator := Map.GetMapIterator;
+        while not MapIterator.EOF do
+        begin
+            Put(MapIterator.CurrentKey, MapIterator.CurrentItem);
+            MapIterator.Next;
+        end;
+    end;
+end;
+
+destructor TAbstractMap.Destroy;
+begin
+    FKeyComparator := nil;
+    FAssociationComparator := nil;
+    inherited Destroy;
+end;
+
+procedure TAbstractMap.InitFrom(const Collection: ICollection);
+var
+    Map: IMap;
+begin
+    inherited InitFrom(Collection);
+    if Collection.QueryInterface(IMap, Map) = S_OK then
+    begin
+        FNaturalKeysOnly := Map.GetNaturalKeysOnly or GetAlwaysNaturalKeys;
+        KeyComparator := Map.GetKeyComparator;
+    end;
+end;
+
+function TAbstractMap.TrueAdd(const Item: ICollectable): Boolean;
+var
+    Position: TCollectionPosition;
+    Mappable: IMappable;
+begin
+    if IsNaturalItem(Item) then
+    begin
+        Mappable := Item as IMappable;
+        Position := GetKeyPosition(Mappable.GetKey);
+        try
+            if Position.Found then
+            begin
+                CollectionError(ceDuplicateKey);
+                Result := false;
+            end
+            else
+            begin
+                TruePut(Position, TAssociation.Create(Mappable.GetKey, Item));
+                Result := true;
+            end;
+        finally
+            Position.Free;
+        end;
+    end
+    else
+    begin
+        CollectionError(ceNotNaturalItem);
+        Result := false;
+    end;
+end;
+
+function TAbstractMap.TrueContains(const Item: ICollectable): Boolean;
+var
+    Item2: ICollectable;
+    Success: Boolean;
+    Iterator: IIterator;
+begin
+    Iterator := GetIterator;
+    Success := false;
+    while not Iterator.EOF and not Success do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+            Success := true;
+        Iterator.Next;
+    end;
+    Result := Success;
+end;
+
+function TAbstractMap.TrueRemove(const Item: ICollectable): ICollectable;
+var
+    Item2: ICollectable;
+    Iterator: IMapIterator;
+    Found: Boolean;
+begin
+    // Sequential search
+    Found := false;
+    Result := nil;
+    Iterator := GetAssociationIterator;
+    while not Iterator.EOF and not Found do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+        begin
+            Result := Item2;
+            Iterator.Remove;
+            Found := true;
+        end;
+        Iterator.Next;
+    end;
+end;
+
+function TAbstractMap.TrueRemoveAll(const Item: ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    Item2: ICollectable;
+    Iterator: IMapIterator;
+begin
+    // Sequential search
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := GetAssociationIterator;
+    while not Iterator.EOF do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+        begin
+            ResultCollection.Add(Item2);
+            Iterator.Remove;
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+class function TAbstractMap.GetAlwaysNaturalKeys: Boolean;
+begin
+    Result := false;
+end;
+
+function TAbstractMap.GetItem(const Key: ICollectable): ICollectable;
+begin
+    Result := Get(Key);
+end;
+
+procedure TAbstractMap.SetItem(const Key, Item: ICollectable);
+begin
+    Put(Key, Item);
+end;
+
+function TAbstractMap.GetIterator: IIterator;
+begin
+    Result := GetAssociationIterator;
+end;
+
+function TAbstractMap.GetKeyComparator: IComparator;
+begin
+    Result := FKeyComparator;
+end;
+
+procedure TAbstractMap.SetKeyComparator(const Value: IComparator);
+begin
+    FKeyComparator := Value;
+    FAssociationComparator.KeyComparator := Value;
+end;
+
+function TAbstractMap.GetKeyIterator: IIterator;
+begin
+    Result := TAssociationKeyIterator.Create(GetAssociationIterator);
+end;
+
+function TAbstractMap.GetKeys: ISet;
+var
+    ResultCollection: TPArraySet;
+    KeyIterator: IIterator;
+begin
+    ResultCollection := TPArraySet.Create(NaturalKeysOnly);
+    ResultCollection.SetComparator(GetKeyComparator);
+    KeyIterator := GetKeyIterator;
+    while not KeyIterator.EOF do
+    begin
+        ResultCollection.Add(KeyIterator.CurrentItem);
+        KeyIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractMap.GetMapIterator: IMapIterator;
+begin
+    Result := GetAssociationIterator;
+end;
+
+function TAbstractMap.GetMapIteratorByKey(const Filter: IFilter): IMapIterator;
+var
+    Iterator: IMapIterator;
+begin
+    Iterator := GetMapIterator;
+    Result := TKeyFilterMapIterator.Create(Iterator, Filter, Iterator.GetAllowRemoval);
+end;
+
+function TAbstractMap.GetMapIteratorByKey(FilterFunc: TCollectionFilterFunc): IMapIterator;
+var
+    Iterator: IMapIterator;
+begin
+    Iterator := GetMapIterator;
+    Result := TKeyFilterFuncMapIterator.Create(Iterator, FilterFunc, Iterator.GetAllowRemoval);
+end;
+
+function TAbstractMap.GetNaturalItemIID: TGUID;
+begin
+    Result := MappableIID;
+end;
+
+function TAbstractMap.GetNaturalKeyIID: TGUID;
+begin
+    Result := EquatableIID;
+end;
+
+function TAbstractMap.GetNaturalKeysOnly: Boolean;
+begin
+    Result := FNaturalKeysOnly;
+end;
+
+function TAbstractMap.GetType: TCollectionType;
+begin
+    Result := ctMap;
+end;
+
+function TAbstractMap.GetValues: ICollection;
+var
+    ResultCollection: ICollection;
+    ValueIterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    ValueIterator := GetIterator;
+    while not ValueIterator.EOF do
+    begin
+        ResultCollection.Add(ValueIterator.CurrentItem);
+        ValueIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+// Overrides TAbstractCollection function, otherwise Create(ICollection) is
+// called, which cannot access keys.
+function TAbstractMap.Clone: ICollection;
+begin
+    Result := (TAbstractMapClass(ClassType)).Create(Self);
+end;
+
+function TAbstractMap.CloneAsMap: IMap;
+begin
+    Result := (TAbstractMapClass(ClassType)).Create(Self);
+end;
+
+function TAbstractMap.ContainsKey(const Key: ICollectable): Boolean;
+var
+    Position: TCollectionPosition;
+begin
+    Position := GetKeyPosition(Key);
+    try
+        Result := Position.Found;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractMap.ContainsKey(const KeyArray: array of ICollectable): Boolean;
+var
+    I: Integer;
+    Success: Boolean;
+begin
+    Success := true;
+    for I := Low(KeyArray) to High(KeyArray) do
+    begin
+        Success := Success and ContainsKey(KeyArray[I]);
+        if not Success then
+            break;
+    end;
+    Result := Success;
+end;
+
+function TAbstractMap.ContainsKey(const Collection: ICollection): Boolean;
+var
+    Iterator: IIterator;
+    Success: Boolean;
+begin
+    Success := true;
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Success := Success and ContainsKey(Iterator.CurrentItem);
+        if not Success then
+            break;
+        Iterator.Next;
+    end;
+    Result := Success;
+end;
+
+function TAbstractMap.Get(const Key: ICollectable): ICollectable;
+var
+    KeyError: TCollectionError;
+    Position: TCollectionPosition;
+begin
+    KeyError := KeyAllowed(Key);
+    if KeyError <> ceOK then
+    begin
+        CollectionError(KeyError);
+        Result := nil;
+    end
+    else
+    begin
+        Position := GetKeyPosition(Key);
+        try
+            if Position.Found then
+                Result := TrueGet(Position).GetValue
+            else
+                Result := nil;
+        finally
+            Position.Free;
+        end;
+    end;
+end;
+
+function TAbstractMap.KeyAllowed(const Key: ICollectable): TCollectionError;
+begin
+    if NaturalKeysOnly and not IsNaturalKey(Key) then
+        Result := ceNotNaturalItem
+    else if Key = nil then
+        Result := ceNilNotAllowed
+    else
+        Result := ceOK;
+end;
+
+function TAbstractMap.IsNaturalKey(const Key: ICollectable): Boolean;
+var
+    Temp: IUnknown;
+begin
+    if Key.QueryInterface(NaturalKeyIID, Temp) <> E_NOINTERFACE then
+        Result := true
+    else
+        Result := false;
+end;
+
+function TAbstractMap.IsNilAllowed: Boolean;
+begin
+    Result := true;
+end;
+
+function TAbstractMap.MatchingKey(const KeyArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(KeyArray) to High(KeyArray) do
+    begin
+        if ContainsKey(KeyArray[I]) then
+            ResultCollection.Add(KeyArray[I]);
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractMap.MatchingKey(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    Iterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        if ContainsKey(Iterator.CurrentItem) then
+            ResultCollection.Add(Iterator.CurrentItem);
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractMap.Put(const Item: ICollectable): ICollectable;
+var
+    Mappable: IMappable;
+    OldAssociation, NewAssociation: IAssociation;
+    Position: TCollectionPosition;
+begin
+    if not IsNaturalItem(Item) then
+    begin
+        CollectionError(ceNotNaturalItem);
+        Result := nil;
+    end
+    else
+    begin
+        Item.QueryInterface(IMappable, Mappable);
+        Position := GetKeyPosition(Mappable.GetKey);
+        try
+            NewAssociation := TAssociation.Create(Mappable.GetKey, Item);
+            OldAssociation := TruePut(Position, NewAssociation);
+            if OldAssociation <> nil then
+                Result := OldAssociation.GetValue
+            else
+                Result := nil;
+        finally
+            Position.Free;
+        end;
+    end;
+end;
+
+function TAbstractMap.Put(const Key, Item: ICollectable): ICollectable;
+var
+    OldAssociation, NewAssociation: IAssociation;
+    ItemError, KeyError: TCollectionError;
+    Position: TCollectionPosition;
+begin
+    ItemError := ItemAllowed(Item);
+    KeyError := KeyAllowed(Key);
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Result := nil;
+    end
+    else if KeyError <> ceOK then
+    begin
+        CollectionError(KeyError);
+        Result := nil;
+    end
+    else
+    begin
+        // Find appropriate place, then place key-item association there
+        Position := GetKeyPosition(Key);
+        try
+            NewAssociation := TAssociation.Create(Key, Item);
+            OldAssociation := TruePut(Position, NewAssociation);
+            if OldAssociation <> nil then
+                Result := OldAssociation.GetValue
+            else
+                Result := nil;
+        finally
+            Position.Free;
+        end;
+    end;
+end;
+
+function TAbstractMap.Put(const ItemArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    Mappable: IMappable;
+    OldAssociation, NewAssociation: IAssociation;
+    Position: TCollectionPosition;
+    Item: ICollectable;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(ItemArray) to High(ItemArray) do
+    begin
+        Item := ItemArray[I];
+        if not IsNaturalItem(Item) then
+        begin
+            CollectionError(ceNotNaturalItem);
+        end
+        else
+        begin
+            // Find appropriate place, then place key-item association there
+            Item.QueryInterface(IMappable, Mappable);
+            Position := GetKeyPosition(Mappable.GetKey);
+            try
+                NewAssociation := TAssociation.Create(Mappable.GetKey, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractMap.Put(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    Mappable: IMappable;
+    OldAssociation, NewAssociation: IAssociation;
+    Position: TCollectionPosition;
+    Iterator: IIterator;
+    Item: ICollectable;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Item := Iterator.CurrentItem;;
+        if not IsNaturalItem(Item) then
+        begin
+            CollectionError(ceNotNaturalItem);
+        end
+        else
+        begin
+            // Find appropriate place, then place key-item association there
+            Item.QueryInterface(IMappable, Mappable);
+            Position := GetKeyPosition(Mappable.GetKey);
+            try
+                NewAssociation := TAssociation.Create(Mappable.GetKey, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractMap.Put(const Map: IMap): ICollection;
+var
+    ResultCollection: ICollection;
+    OldAssociation, NewAssociation: IAssociation;
+    ItemError, KeyError: TCollectionError;
+    Position: TCollectionPosition;
+    MapIterator: IMapIterator;
+    Key, Item: ICollectable;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    MapIterator := Map.GetMapIterator;
+    while not MapIterator.EOF do
+    begin
+        Key := MapIterator.CurrentKey;
+        Item := MapIterator.CurrentItem;
+
+        ItemError := ItemAllowed(Item);
+        KeyError := KeyAllowed(Key);
+        if ItemError <> ceOK then
+        begin
+            CollectionError(ItemError);
+        end
+        else if KeyError <> ceOK then
+        begin
+            CollectionError(KeyError);
+        end
+        else
+        begin
+            // Find appropriate place, then place key-item association there
+            Position := GetKeyPosition(Key);
+            try
+                NewAssociation := TAssociation.Create(Key, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+        MapIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractMap.RemoveKey(const Key: ICollectable): ICollectable;
+var
+    KeyError: TCollectionError;
+    Position: TCollectionPosition;
+    OldAssociation: IAssociation;
+begin
+    KeyError := KeyAllowed(Key);
+    if KeyError <> ceOK then
+    begin
+        CollectionError(KeyError);
+        Result := nil;
+    end
+    else
+    begin
+        Position := GetKeyPosition(Key);
+        try
+            if Position.Found then
+            begin
+                OldAssociation := TrueRemove2(Position);
+                Result := OldAssociation.GetValue
+            end
+            else
+                Result := nil;
+        finally
+            Position.Free;
+        end;
+    end;
+end;
+
+function TAbstractMap.RemoveKey(const KeyArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    OldAssociation: IAssociation;
+    KeyError: TCollectionError;
+    Position: TCollectionPosition;
+    Key: ICollectable;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(KeyArray) to High(KeyArray) do
+    begin
+        Key := KeyArray[I];
+        KeyError := KeyAllowed(Key);
+        if KeyError <> ceOK then
+        begin
+            CollectionError(KeyError);
+        end
+        else
+        begin
+            Position := GetKeyPosition(Key);
+            try
+                if Position.Found then
+                begin
+                    OldAssociation := TrueRemove2(Position);
+                    ResultCollection.Add(OldAssociation.GetValue);
+                end;
+            finally
+                Position.Free;
+            end;
+        end;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractMap.RemoveKey(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    OldAssociation: IAssociation;
+    KeyError: TCollectionError;
+    Position: TCollectionPosition;
+    Key: ICollectable;
+    Iterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Key := Iterator.CurrentItem;
+        KeyError := KeyAllowed(Key);
+        if KeyError <> ceOK then
+        begin
+            CollectionError(KeyError);
+        end
+        else
+        begin
+            Position := GetKeyPosition(Key);
+            try
+                if Position.Found then
+                begin
+                    OldAssociation := TrueRemove2(Position);
+                    ResultCollection.Add(OldAssociation.GetValue);
+                end;
+            finally
+                Position.Free;
+            end;
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractMap.RetainKey(const KeyArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    MapIterator: IMapIterator;
+    I: Integer;
+    Found: Boolean;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+    end
+    else
+    begin
+        MapIterator := GetMapIterator;
+        while not MapIterator.EOF do
+        begin
+            // Converting the array to a map would be faster but I don't want to
+            // couple base class code to a complex collection.
+            Found := false;
+            for I := Low(KeyArray) to High(KeyArray) do
+            begin
+                Found := KeyComparator.Equals(MapIterator.CurrentKey, KeyArray[I]);
+                if Found then
+                    break;
+            end;
+            if not Found then
+            begin
+                ResultCollection.Add(MapIterator.CurrentItem);
+                MapIterator.Remove;
+            end;
+            MapIterator.Next;
+        end;
+        Result := ResultCollection;
+    end;
+end;
+
+function TAbstractMap.RetainKey(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    MapIterator: IMapIterator;
+    Key: ICollectable;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+    end
+    else
+    begin
+        MapIterator := GetMapIterator;
+        while not MapIterator.EOF do
+        begin
+            Key := MapIterator.CurrentKey;
+            if not Collection.Contains(Key) then
+            begin
+                ResultCollection.Add(MapIterator.CurrentItem);
+                MapIterator.Remove;
+            end;
+            MapIterator.Next;
+        end;
+    end;
+    Result := ResultCollection;
+end;
+
+
+{ TAbstractIntegerMap }
+constructor TAbstractIntegerMap.Create(NaturalItemsOnly: Boolean);
+begin
+    inherited Create(NaturalItemsOnly);
+    FAssociationComparator := TIntegerAssociationComparator.Create;
+end;
+
+constructor TAbstractIntegerMap.Create(const ItemArray: array of ICollectable);
+begin
+    Create(ItemArray, true);
+end;
+
+constructor TAbstractIntegerMap.Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean);
+begin
+    inherited Create(ItemArray, true);
+end;
+
+constructor TAbstractIntegerMap.Create(const KeyArray: array of Integer; const ItemArray: array of ICollectable);
+begin
+    Create(KeyArray, ItemArray, false);
+end;
+
+constructor TAbstractIntegerMap.Create(const KeyArray: array of Integer; const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean);
+var
+    I, Lo, Hi: Integer;
+begin
+    Create(NaturalItemsOnly);
+    Capacity := Min(Length(KeyArray), Length(ItemArray));
+    if not FixedSize then
+    begin
+        Lo := Max(Low(KeyArray), Low(ItemArray));
+        Hi := Min(High(KeyArray), High(ItemArray));
+        for I := Lo to Hi do
+        begin
+            Put(KeyArray[I], ItemArray[I]);
+        end;
+    end;
+end;
+
+constructor TAbstractIntegerMap.Create(const Map: IIntegerMap);
+var
+    MapIterator: IIntegerMapIterator;
+begin
+    Create(Map.GetNaturalItemsOnly);
+    InitFrom(Map);
+    Capacity := Map.GetSize;
+    if not FixedSize then
+    begin
+        MapIterator := Map.GetMapIterator;
+        while not MapIterator.EOF do
+        begin
+            Put(MapIterator.CurrentKey, MapIterator.CurrentItem);
+            MapIterator.Next;
+        end;
+    end;
+end;
+
+destructor TAbstractIntegerMap.Destroy;
+begin
+    FAssociationComparator := nil;
+    inherited Destroy;
+end;
+
+function TAbstractIntegerMap.TrueAdd(const Item: ICollectable): Boolean;
+var
+    Position: TCollectionPosition;
+    Mappable: IIntegerMappable;
+begin
+    if IsNaturalItem(Item) then
+    begin
+        Mappable := Item as IIntegerMappable;
+        Position := GetKeyPosition(Mappable.GetKey);
+        try
+            if Position.Found then
+            begin
+                CollectionError(ceDuplicateKey);
+                Result := false;
+            end
+            else
+            begin
+                TruePut(Position, TIntegerAssociation.Create(Mappable.GetKey, Item));
+                Result := true;
+            end;
+        finally
+            Position.Free;
+        end;
+    end
+    else
+    begin
+        CollectionError(ceNotNaturalItem);
+        Result := false;
+    end;
+end;
+
+function TAbstractIntegerMap.TrueContains(const Item: ICollectable): Boolean;
+var
+    Item2: ICollectable;
+    Success: Boolean;
+    Iterator: IIterator;
+begin
+    Iterator := GetIterator;
+    Success := false;
+    while not Iterator.EOF and not Success do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+            Success := true;
+        Iterator.Next;
+    end;
+    Result := Success;
+end;
+
+function TAbstractIntegerMap.TrueRemove(const Item: ICollectable): ICollectable;
+var
+    Item2: ICollectable;
+    Iterator: IIntegerMapIterator;
+    Found: Boolean;
+begin
+    // Sequential search
+    Found := false;
+    Result := nil;
+    Iterator := GetAssociationIterator;
+    while not Iterator.EOF and not Found do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+        begin
+            Result := Item2;
+            Iterator.Remove;
+            Found := true;
+        end;
+        Iterator.Next;
+    end;
+end;
+
+function TAbstractIntegerMap.TrueRemoveAll(const Item: ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    Item2: ICollectable;
+    Iterator: IIntegerMapIterator;
+begin
+    // Sequential search
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := GetAssociationIterator;
+    while not Iterator.EOF do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+        begin
+            ResultCollection.Add(Item2);
+            Iterator.Remove;
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractIntegerMap.GetItem(const Key: Integer): ICollectable;
+begin
+    Result := Get(Key);
+end;
+
+procedure TAbstractIntegerMap.SetItem(const Key: Integer; const Item: ICollectable);
+begin
+    Put(Key, Item);
+end;
+
+function TAbstractIntegerMap.GetIterator: IIterator;
+begin
+    Result := GetAssociationIterator;
+end;
+
+function TAbstractIntegerMap.GetKeys: ISet;
+var
+    ResultCollection: TPArraySet;
+    MapIterator: IIntegerMapIterator;
+begin
+    ResultCollection := TPArraySet.Create(true);
+    MapIterator := GetMapIterator;
+    while not MapIterator.EOF do
+    begin
+        ResultCollection.Add(TIntegerWrapper.Create(MapIterator.CurrentKey) as ICollectable);
+        MapIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractIntegerMap.GetMapIterator: IIntegerMapIterator;
+begin
+    Result := GetAssociationIterator;
+end;
+
+function TAbstractIntegerMap.GetNaturalItemIID: TGUID;
+begin
+    Result := IntegerMappableIID;
+end;
+
+function TAbstractIntegerMap.GetType: TCollectionType;
+begin
+    Result := ctIntegerMap;
+end;
+
+function TAbstractIntegerMap.GetValues: ICollection;
+var
+    ResultCollection: ICollection;
+    ValueIterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    ValueIterator := GetIterator;
+    while not ValueIterator.EOF do
+    begin
+        ResultCollection.Add(ValueIterator.CurrentItem);
+        ValueIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+// Overrides TAbstractCollection function, otherwise Create(ICollection) is
+// called, which cannot access keys.
+function TAbstractIntegerMap.Clone: ICollection;
+begin
+    Result := (TAbstractIntegerMapClass(ClassType)).Create(Self);
+end;
+
+function TAbstractIntegerMap.CloneAsIntegerMap: IIntegerMap;
+begin
+    Result := (TAbstractIntegerMapClass(ClassType)).Create(Self);
+end;
+
+function TAbstractIntegerMap.ContainsKey(const Key: Integer): Boolean;
+var
+    Position: TCollectionPosition;
+begin
+    Position := GetKeyPosition(Key);
+    try
+        Result := Position.Found;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractIntegerMap.ContainsKey(const KeyArray: array of Integer): Boolean;
+var
+    I: Integer;
+    Success: Boolean;
+begin
+    Success := true;
+    for I := Low(KeyArray) to High(KeyArray) do
+    begin
+        Success := Success and ContainsKey(KeyArray[I]);
+        if not Success then
+            break;
+    end;
+    Result := Success;
+end;
+
+function TAbstractIntegerMap.Get(const Key: Integer): ICollectable;
+var
+    Position: TCollectionPosition;
+begin
+    Position := GetKeyPosition(Key);
+    try
+        if Position.Found then
+            Result := TrueGet(Position).GetValue
+        else
+            Result := nil;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractIntegerMap.IsNilAllowed: Boolean;
+begin
+    Result := true;
+end;
+
+function TAbstractIntegerMap.Put(const Item: ICollectable): ICollectable;
+var
+    Mappable: IIntegerMappable;
+    OldAssociation, NewAssociation: IIntegerAssociation;
+    Position: TCollectionPosition;
+begin
+    if not IsNaturalItem(Item) then
+    begin
+        CollectionError(ceNotNaturalItem);
+        Result := nil;
+    end
+    else
+    begin
+        Item.QueryInterface(IIntegerMappable, Mappable);
+        Position := GetKeyPosition(Mappable.GetKey);
+        try
+            NewAssociation := TIntegerAssociation.Create(Mappable.GetKey, Item);
+            OldAssociation := TruePut(Position, NewAssociation);
+            if OldAssociation <> nil then
+                Result := OldAssociation.GetValue
+            else
+                Result := nil;
+        finally
+            Position.Free;
+        end;
+    end;
+end;
+
+function TAbstractIntegerMap.Put(const Key: Integer; const Item: ICollectable): ICollectable;
+var
+    OldAssociation, NewAssociation: IIntegerAssociation;
+    ItemError: TCollectionError;
+    Position: TCollectionPosition;
+begin
+    ItemError := ItemAllowed(Item);
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Result := nil;
+    end
+    else
+    begin
+        Position := GetKeyPosition(Key);
+        try
+            NewAssociation := TIntegerAssociation.Create(Key, Item);
+            OldAssociation := TruePut(Position, NewAssociation);
+            if OldAssociation <> nil then
+                Result := OldAssociation.GetValue
+            else
+                Result := nil;
+        finally
+            Position.Free;
+        end;
+    end;
+end;
+
+function TAbstractIntegerMap.Put(const ItemArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    Mappable: IIntegerMappable;
+    OldAssociation, NewAssociation: IIntegerAssociation;
+    Position: TCollectionPosition;
+    Item: ICollectable;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(ItemArray) to High(ItemArray) do
+    begin
+        Item := ItemArray[I];
+        if not IsNaturalItem(Item) then
+        begin
+            CollectionError(ceNotNaturalItem);
+        end
+        else
+        begin
+            Item.QueryInterface(IIntegerMappable, Mappable);
+            Position := GetKeyPosition(Mappable.GetKey);
+            try
+                NewAssociation := TIntegerAssociation.Create(Mappable.GetKey, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractIntegerMap.Put(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    Mappable: IIntegerMappable;
+    OldAssociation, NewAssociation: IIntegerAssociation;
+    Position: TCollectionPosition;
+    Iterator: IIterator;
+    Item: ICollectable;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Item := Iterator.CurrentItem;;
+        if not IsNaturalItem(Item) then
+        begin
+            CollectionError(ceNotNaturalItem);
+        end
+        else
+        begin
+            Item.QueryInterface(IIntegerMappable, Mappable);
+            Position := GetKeyPosition(Mappable.GetKey);
+            try
+                NewAssociation := TIntegerAssociation.Create(Mappable.GetKey, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractIntegerMap.Put(const Map: IIntegerMap): ICollection;
+var
+    ResultCollection: ICollection;
+    OldAssociation, NewAssociation: IIntegerAssociation;
+    ItemError: TCollectionError;
+    Position: TCollectionPosition;
+    MapIterator: IIntegerMapIterator;
+    Item: ICollectable;
+    Key: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    MapIterator := Map.GetMapIterator;
+    while not MapIterator.EOF do
+    begin
+        Key := MapIterator.CurrentKey;
+        Item := MapIterator.CurrentItem;
+
+        ItemError := ItemAllowed(Item);
+        if ItemError <> ceOK then
+        begin
+            CollectionError(ItemError);
+        end
+        else
+        begin
+            Position := GetKeyPosition(Key);
+            try
+                NewAssociation := TIntegerAssociation.Create(Key, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+        MapIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractIntegerMap.RemoveKey(const Key: Integer): ICollectable;
+var
+    Position: TCollectionPosition;
+    OldAssociation: IIntegerAssociation;
+begin
+    Position := GetKeyPosition(Key);
+    try
+        if Position.Found then
+        begin
+            OldAssociation := TrueRemove2(Position);
+            Result := OldAssociation.GetValue
+        end
+        else
+            Result := nil;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractIntegerMap.RemoveKey(const KeyArray: array of Integer): ICollection;
+var
+    ResultCollection: ICollection;
+    OldAssociation: IIntegerAssociation;
+    Position: TCollectionPosition;
+    Key: Integer;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(KeyArray) to High(KeyArray) do
+    begin
+        Key := KeyArray[I];
+        Position := GetKeyPosition(Key);
+        try
+            if Position.Found then
+            begin
+                OldAssociation := TrueRemove2(Position);
+                ResultCollection.Add(OldAssociation.GetValue);
+            end;
+        finally
+            Position.Free;
+        end;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractIntegerMap.RetainKey(const KeyArray: array of Integer): ICollection;
+var
+    ResultCollection: ICollection;
+    MapIterator: IIntegerMapIterator;
+    I: Integer;
+    Found: Boolean;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+    end
+    else
+    begin
+        MapIterator := GetMapIterator;
+        while not MapIterator.EOF do
+        begin
+            // Converting the array to a map would be faster but I don't want to
+            // couple base class code to a complex collection.
+            Found := false;
+            for I := Low(KeyArray) to High(KeyArray) do
+            begin
+                Found := (MapIterator.CurrentKey = KeyArray[I]);
+                if Found then
+                    break;
+            end;
+            if not Found then
+            begin
+                ResultCollection.Add(MapIterator.CurrentItem);
+                MapIterator.Remove;
+            end;
+            MapIterator.Next;
+        end;
+        Result := ResultCollection;
+    end;
+end;
+
+
+{ TAbstractStringMap }
+constructor TAbstractStringMap.Create(NaturalItemsOnly: Boolean);
+begin
+    inherited Create(NaturalItemsOnly);
+    FAssociationComparator := TStringAssociationComparator.Create;
+end;
+
+constructor TAbstractStringMap.Create(const ItemArray: array of ICollectable);
+begin
+    Create(ItemArray, true);
+end;
+
+constructor TAbstractStringMap.Create(const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean);
+begin
+    inherited Create(ItemArray, true);
+end;
+
+constructor TAbstractStringMap.Create(const KeyArray: array of String; const ItemArray: array of ICollectable);
+begin
+    Create(KeyArray, ItemArray, false);
+end;
+
+constructor TAbstractStringMap.Create(const KeyArray: array of String; const ItemArray: array of ICollectable; NaturalItemsOnly: Boolean);
+var
+    I, Lo, Hi: Integer;
+begin
+    Create(NaturalItemsOnly);
+    Capacity := Min(Length(KeyArray), Length(ItemArray));
+    if not FixedSize then
+    begin
+        Lo := Max(Low(KeyArray), Low(ItemArray));
+        Hi := Min(High(KeyArray), High(ItemArray));
+        for I := Lo to Hi do
+        begin
+            Put(KeyArray[I], ItemArray[I]);
+        end;
+    end;
+end;
+
+constructor TAbstractStringMap.Create(const Map: IStringMap);
+var
+    MapIterator: IStringMapIterator;
+begin
+    Create(Map.GetNaturalItemsOnly);
+    InitFrom(Map);
+    Capacity := Map.GetSize;
+    if not FixedSize then
+    begin
+        MapIterator := Map.GetMapIterator;
+        while not MapIterator.EOF do
+        begin
+            Put(MapIterator.CurrentKey, MapIterator.CurrentItem);
+            MapIterator.Next;
+        end;
+    end;
+end;
+
+destructor TAbstractStringMap.Destroy;
+begin
+    FAssociationComparator := nil;
+    inherited Destroy;
+end;
+
+function TAbstractStringMap.TrueAdd(const Item: ICollectable): Boolean;
+var
+    Position: TCollectionPosition;
+    Mappable: IStringMappable;
+begin
+    if IsNaturalItem(Item) then
+    begin
+        Mappable := Item as IStringMappable;
+        Position := GetKeyPosition(Mappable.GetKey);
+        try
+            if Position.Found then
+            begin
+                CollectionError(ceDuplicateKey);
+                Result := false;
+            end
+            else
+            begin
+                TruePut(Position, TStringAssociation.Create(Mappable.GetKey, Item));
+                Result := true;
+            end;
+        finally
+            Position.Free;
+        end;
+    end
+    else
+    begin
+        CollectionError(ceNotNaturalItem);
+        Result := false;
+    end;
+end;
+
+function TAbstractStringMap.TrueContains(const Item: ICollectable): Boolean;
+var
+    Item2: ICollectable;
+    Success: Boolean;
+    Iterator: IIterator;
+begin
+    Iterator := GetIterator;
+    Success := false;
+    while not Iterator.EOF and not Success do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+            Success := true;
+        Iterator.Next;
+    end;
+    Result := Success;
+end;
+
+function TAbstractStringMap.TrueRemove(const Item: ICollectable): ICollectable;
+var
+    Item2: ICollectable;
+    Iterator: IStringMapIterator;
+    Found: Boolean;
+begin
+    // Sequential search
+    Found := false;
+    Result := nil;
+    Iterator := GetAssociationIterator;
+    while not Iterator.EOF and not Found do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+        begin
+            Result := Item2;
+            Iterator.Remove;
+            Found := true;
+        end;
+        Iterator.Next;
+    end;
+end;
+
+function TAbstractStringMap.TrueRemoveAll(const Item: ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    Item2: ICollectable;
+    Iterator: IIterator;
+begin
+    // Sequential search
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := GetAssociationIterator;
+    while not Iterator.EOF do
+    begin
+        Item2 := Iterator.CurrentItem;
+        if Comparator.Equals(Item, Item2) then
+        begin
+            ResultCollection.Add(Item2);
+            Iterator.Remove;
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractStringMap.GetItem(const Key: String): ICollectable;
+begin
+    Result := Get(Key);
+end;
+
+procedure TAbstractStringMap.SetItem(const Key: String; const Item: ICollectable);
+begin
+    Put(Key, Item);
+end;
+
+function TAbstractStringMap.GetIterator: IIterator;
+begin
+    Result := GetAssociationIterator;
+end;
+
+function TAbstractStringMap.GetKeys: ISet;
+var
+    ResultCollection: TPArraySet;
+    MapIterator: IStringMapIterator;
+begin
+    ResultCollection := TPArraySet.Create(true);
+    MapIterator := GetMapIterator;
+    while not MapIterator.EOF do
+    begin
+        ResultCollection.Add(TStringWrapper.Create(MapIterator.CurrentKey) as ICollectable);
+        MapIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractStringMap.GetMapIterator: IStringMapIterator;
+begin
+    Result := GetAssociationIterator;
+end;
+
+function TAbstractStringMap.GetNaturalItemIID: TGUID;
+begin
+    Result := StringMappableIID;
+end;
+
+function TAbstractStringMap.GetType: TCollectionType;
+begin
+    Result := ctStringMap;
+end;
+
+function TAbstractStringMap.GetValues: ICollection;
+var
+    ResultCollection: ICollection;
+    ValueIterator: IIterator;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    ValueIterator := GetIterator;
+    while not ValueIterator.EOF do
+    begin
+        ResultCollection.Add(ValueIterator.CurrentItem);
+        ValueIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+// Overrides TAbstractCollection function, otherwise Create(ICollection) is
+// called, which cannot access keys.
+function TAbstractStringMap.Clone: ICollection;
+begin
+    Result := (TAbstractStringMapClass(ClassType)).Create(Self);
+end;
+
+function TAbstractStringMap.CloneAsStringMap: IStringMap;
+begin
+    Result := (TAbstractStringMapClass(ClassType)).Create(Self);
+end;
+
+function TAbstractStringMap.ContainsKey(const Key: String): Boolean;
+var
+    Position: TCollectionPosition;
+begin
+    Position := GetKeyPosition(Key);
+    try
+        Result := Position.Found;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractStringMap.ContainsKey(const KeyArray: array of String): Boolean;
+var
+    I: Integer;
+    Success: Boolean;
+begin
+    Success := true;
+    for I := Low(KeyArray) to High(KeyArray) do
+    begin
+        Success := Success and ContainsKey(KeyArray[I]);
+        if not Success then
+            break;
+    end;
+    Result := Success;
+end;
+
+function TAbstractStringMap.Get(const Key: String): ICollectable;
+var
+    Position: TCollectionPosition;
+begin
+    Position := GetKeyPosition(Key);
+    try
+        if Position.Found then
+            Result := TrueGet(Position).GetValue
+        else
+            Result := nil;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractStringMap.IsNilAllowed: Boolean;
+begin
+    Result := true;
+end;
+
+function TAbstractStringMap.Put(const Item: ICollectable): ICollectable;
+var
+    Mappable: IStringMappable;
+    OldAssociation, NewAssociation: IStringAssociation;
+    Position: TCollectionPosition;
+begin
+    if not IsNaturalItem(Item) then
+    begin
+        CollectionError(ceNotNaturalItem);
+        Result := nil;
+    end
+    else
+    begin
+        Item.QueryInterface(IStringMappable, Mappable);
+        Position := GetKeyPosition(Mappable.GetKey);
+        try
+            NewAssociation := TStringAssociation.Create(Mappable.GetKey, Item);
+            OldAssociation := TruePut(Position, NewAssociation);
+            if OldAssociation <> nil then
+                Result := OldAssociation.GetValue
+            else
+                Result := nil;
+        finally
+            Position.Free;
+        end;
+    end;
+end;
+
+function TAbstractStringMap.Put(const Key: String; const Item: ICollectable): ICollectable;
+var
+    OldAssociation, NewAssociation: IStringAssociation;
+    ItemError: TCollectionError;
+    Position: TCollectionPosition;
+begin
+    ItemError := ItemAllowed(Item);
+    if ItemError <> ceOK then
+    begin
+        CollectionError(ItemError);
+        Result := nil;
+    end
+    else
+    begin
+        Position := GetKeyPosition(Key);
+        try
+            NewAssociation := TStringAssociation.Create(Key, Item);
+            OldAssociation := TruePut(Position, NewAssociation);
+            if OldAssociation <> nil then
+                Result := OldAssociation.GetValue
+            else
+                Result := nil;
+        finally
+            Position.Free;
+        end;
+    end;
+end;
+
+function TAbstractStringMap.Put(const ItemArray: array of ICollectable): ICollection;
+var
+    ResultCollection: ICollection;
+    Mappable: IStringMappable;
+    OldAssociation, NewAssociation: IStringAssociation;
+    Position: TCollectionPosition;
+    Item: ICollectable;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(ItemArray) to High(ItemArray) do
+    begin
+        Item := ItemArray[I];
+        if not IsNaturalItem(Item) then
+        begin
+            CollectionError(ceNotNaturalItem);
+        end
+        else
+        begin
+            Item.QueryInterface(IStringMappable, Mappable);
+            Position := GetKeyPosition(Mappable.GetKey);
+            try
+                NewAssociation := TStringAssociation.Create(Mappable.GetKey, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractStringMap.Put(const Collection: ICollection): ICollection;
+var
+    ResultCollection: ICollection;
+    Mappable: IStringMappable;
+    OldAssociation, NewAssociation: IStringAssociation;
+    Position: TCollectionPosition;
+    Iterator: IIterator;
+    Item: ICollectable;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    Iterator := Collection.GetIterator;
+    while not Iterator.EOF do
+    begin
+        Item := Iterator.CurrentItem;;
+        if not IsNaturalItem(Item) then
+        begin
+            CollectionError(ceNotNaturalItem);
+        end
+        else
+        begin
+            Item.QueryInterface(IStringMappable, Mappable);
+            Position := GetKeyPosition(Mappable.GetKey);
+            try
+                NewAssociation := TStringAssociation.Create(Mappable.GetKey, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+        Iterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractStringMap.Put(const Map: IStringMap): ICollection;
+var
+    ResultCollection: ICollection;
+    OldAssociation, NewAssociation: IStringAssociation;
+    ItemError: TCollectionError;
+    Position: TCollectionPosition;
+    MapIterator: IStringMapIterator;
+    Item: ICollectable;
+    Key: String;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    MapIterator := Map.GetMapIterator;
+    while not MapIterator.EOF do
+    begin
+        Key := MapIterator.CurrentKey;
+        Item := MapIterator.CurrentItem;
+
+        ItemError := ItemAllowed(Item);
+        if ItemError <> ceOK then
+        begin
+            CollectionError(ItemError);
+        end
+        else
+        begin
+            Position := GetKeyPosition(Key);
+            try
+                NewAssociation := TStringAssociation.Create(Key, Item);
+                OldAssociation := TruePut(Position, NewAssociation);
+                if OldAssociation <> nil then
+                    ResultCollection.Add(OldAssociation.GetValue);
+            finally
+                Position.Free;
+            end;
+        end;
+        MapIterator.Next;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractStringMap.RemoveKey(const Key: String): ICollectable;
+var
+    Position: TCollectionPosition;
+    OldAssociation: IStringAssociation;
+begin
+    Position := GetKeyPosition(Key);
+    try
+        if Position.Found then
+        begin
+            OldAssociation := TrueRemove2(Position);
+            Result := OldAssociation.GetValue
+        end
+        else
+            Result := nil;
+    finally
+        Position.Free;
+    end;
+end;
+
+function TAbstractStringMap.RemoveKey(const KeyArray: array of String): ICollection;
+var
+    ResultCollection: ICollection;
+    OldAssociation: IStringAssociation;
+    Position: TCollectionPosition;
+    Key: String;
+    I: Integer;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    for I := Low(KeyArray) to High(KeyArray) do
+    begin
+        Key := KeyArray[I];
+        Position := GetKeyPosition(Key);
+        try
+            if Position.Found then
+            begin
+                OldAssociation := TrueRemove2(Position);
+                ResultCollection.Add(OldAssociation.GetValue);
+            end;
+        finally
+            Position.Free;
+        end;
+    end;
+    Result := ResultCollection;
+end;
+
+function TAbstractStringMap.RetainKey(const KeyArray: array of String): ICollection;
+var
+    ResultCollection: ICollection;
+    MapIterator: IStringMapIterator;
+    I: Integer;
+    Found: Boolean;
+begin
+    ResultCollection := TPArrayBag.Create(NaturalItemsOnly);
+    if FixedSize then
+    begin
+        CollectionError(ceFixedSize);
+    end
+    else
+    begin
+        MapIterator := GetMapIterator;
+        while not MapIterator.EOF do
+        begin
+            // Converting the array to a map would be faster but I don't want to
+            // couple base class code to a complex collection.
+            Found := false;
+            for I := Low(KeyArray) to High(KeyArray) do
+            begin
+                Found := (MapIterator.CurrentKey = KeyArray[I]);
+                if Found then
+                    break;
+            end;
+            if not Found then
+            begin
+                ResultCollection.Add(MapIterator.CurrentItem);
+                MapIterator.Remove;
+            end;
+            MapIterator.Next;
+        end;
+        Result := ResultCollection;
+    end;
+end;
+
+
+{ ECollectionError }
+constructor ECollectionError.Create(const Msg: String; const Collection: ICollection; ErrorType: TCollectionError);
+begin
+    inherited Create(Msg);
+    FCollection := Collection;
+    FErrorType := ErrorType;
+end;
+
+{ TAbstractListIterator }
+constructor TAbstractListIterator.Create(Collection: TAbstractList);
+begin
+    inherited Create(true);
+    FCollection := Collection;
+    First;
+end;
+
+function TAbstractListIterator.TrueFirst: ICollectable;
+begin
+    FIndex := 0;
+    if FIndex < FCollection.GetSize then
+        Result := FCollection.GetItem(FIndex)
+    else
+        Result := nil;
+end;
+
+function TAbstractListIterator.TrueNext: ICollectable;
+begin
+    Inc(FIndex);
+    if FIndex < FCollection.GetSize then
+        Result := FCollection.GetItem(FIndex)
+    else
+        Result := nil;
+end;
+
+procedure TAbstractListIterator.TrueRemove;
+begin
+    FCollection.Delete(FIndex);
+    Dec(FIndex);
+end;
+
+end.