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TList

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Ivan Semenkov edited this page Aug 8, 2021 · 3 revisions

Table of contents

About

A doubly-linked list stores a collection of values. Each entry in the list contains a link to the next entry and the previous entry. It is therefore possible to iterate over entries in the list in either direction.

uses container.list, utils.functor; type generic TList<T, BinaryCompareFunctor> = class

BinaryCompareFunctor is based on utils.functor.TBinaryFunctor interface and used to compare two array items in sort and search functions.

TOptionalValue

If macro {$USE_OPTIONAL} is defined, then all methods return a TOptionalValue wrapper, otherwise T.

uses utils.optional; type TOptionalValue = {$IFDEF FPC}specialize{$ENDIF} TOptional<T>;

For non-existent values, returns a empty TOptionalValue if defined or an EValueNotExistsException is thrown.

type {$IFNDEF USE_OPTIONAL} EValueNotExistsException = class(Exception); {$ENDIF}

Create

A new list can be created by call its constructor.

constructor Create;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; begin list := TIntegerList.Create; FreeAndNil(list); end;

Insert

There are several methods to insert data to the list.

Append

Append a value to the end of a TList. Return true if the request was successful, false if it was not possible to add the new entry.

function Append (AValue : T) : Boolean;
Example
uses container.list, utils.functor; type IntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger var list : TIntegerList; begin list := TIntegerList.Create; list.Append(15); list.Append(-598565101); FreeAndNil(list); end;

Prepend

Prepend a value to the beginning of a TList. Return true if the request was successful, false if it was not possible to add the new entry.

function Prepend (AValue : T) : Boolean;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; begin list := TIntegerList.Create; list.Prepend(12); list.Prepend(-54); FreeAndNil(list); end;

Remove

The methods to remove data from the list.

Remove

Remove all occurrences of a particular value from a list. Return the number of entries removed from the list.

function Remove (AData: T) : Cardinal;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; begin list := TIntegerList.Create; list.Remove(0); list.Remove(8); FreeAndNil(list); end;

Clear

Remove all entries from a TList.

procedure Clear;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; begin list := TIntegerList.Create; list.Clear; FreeAndNil(list); end;

Search

The methods to find data in the list.

FindEntry

Find the entry for a particular value in a list. Return TIterator.

function FindEntry (AData : T) : TIterator;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; iterator := list.FindEntry(5); if iterator.HasValue then writeln(iterator.Value); FreeAndNil(list); end;

NthEntry

Retrieve the entry at a specified index in a list.

function NthEntry (AIndex : Cardinal) : TIterator;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; iterator := list.NthEntry(5); if iterator.HasValue then writeln(iterator.Value); FreeAndNil(list); end;

Sort

Sort the values in a TList.

procedure Sort;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; begin list := TIntegerList.Create; list.Sort; FreeAndNil(list); end;

Length

Return TList size.

property Length : Cardinal;

IsEmpty

Return true if container is empty.

function IsEmpty : Boolean;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; if list.IsEmpty then ; FreeAndNil(list); end;

Iterate

It is possible to iterate for TList values using in operator. Each value would present as TList.TIterator object.

uses container.list, utils.functor; type generic TList<T, BinaryCompareFunctor> = class type TIterator = class({$IFDEF FPC}specialize{$ENDIF} TBidirectionalIterator<T, TIterator>) end;

TBidirectionalIterator is a abstract class which provide interface for iterable object that can moves to both sides.

For ... in ...

Use for ... in ... operator for iterates over container items.

Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; val : Integer; begin list := TIntegerList.Create; for val in list do ; FreeAndNil(list); end;

FirstEntry

Retrive the iterator for first entry in a list.

function FirstEntry : TIterator;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; iterator := list.FirstEntry; FreeAndNil(list); end;

LastEntry

Retrive the iterator for last entry in a list.

function LastEntry : TIterator;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; iterator := list.LastEntry; FreeAndNil(list); end;

TIterator

HasValue

Return true if iterator has correct value.

function HasValue : Boolean;
Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; iterator := list.FirstEntry; while iterator.HasValue do begin iterator := iterator.Next; end; FreeAndNil(list); end;
Prev

Retrieve the iterator for previous entry in a list.

Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; iterator := list.LastEntry; while iterator.HasValue do begin iterator := iterator.Prev; end; FreeAndNil(list); end;
Next

Retrieve the iterator for next entry in a list.

Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; iterator := list.FirstEntry; while iterator.HasValue do begin iterator := iterator.Next; end; FreeAndNil(list); end;
Value

To get/set value use Value property.

property Value : {$IFNDEF USE_OPTIONAL}T{$ELSE}TOptionalValue{$ENDIF};

If iterator not have correct value returns empty TOptionalValue or raise EValueNotExistsException.

Example
uses container.list, utils.functor; type TIntegerList = {$IFDEF FPC}type specialize{$ENDIF} TList<Integer, TCompareFunctorInteger>; var list : TIntegerList; iterator : TIntegerList.TIterator; begin list := TIntegerList.Create; iterator := list.FirstEntry; while iterator.HasValue do begin	writeln(iterator.Value); iterator := iterator.Next; end; FreeAndNil(list); end;

Additional

TFilterEnumerator

Class provides filtering enumerator by TUnaryFunctor.

More details read on wiki page.

TAccumulate

Accumulate iterable object data using functor.

More details read on wiki page.

TMap

Map applying the given functor to each item of a given iterable object.

More details read on wiki page.

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