Which Delphi data structure can hold a list of unique integers?

Question

When I approach Java problems, I use the collection pattern. However, doing it in Delphi is quite a nightmare since there is no Integer object to handle things.

I need a data structure that holds numbers. I want to be able to add numbers, remove numbers, and check the contents of the collection, and each number must be unique.

I'm not interested in a solution I need to implement and test for bugs myself. Is there a ready object like Java's HashTable?

Answer 1

uses GpLists;

var
  numberList: TGpIntegerList;
begin
  numberList := TGpIntegerList.Create;
  numberList.Duplicates := dupIgnore;
  numberList.Sorted := true;
  numberList.add(1);
  numberList.add(2);
  numberList.add(3);
  numberList.add(1);

GpLists comes with a BSD license. It also contains a class holding 64-bit integers - TGpInt64List - and bunch of other stuff.

Answer 2

Dictionary<Integer,Boolean> or similar would do.

Answer 3

I know it's dirty, but you could misuse TStringList (or THashedStringList).

var
  numberList: TStringList;
begin
  numberList := TStringList.Create;
  numberList.Duplicates := dupIgnore;
  numberList.Sorted := true;
  numberList.add(IntToStr(1));
  numberList.add(IntToStr(2));
  numberList.add(IntToStr(3));
  numberList.add(IntToStr(1));
  // numberList.CommaText = '1,2,3'

Answer 4

This is a simple solution for the Delphi version with generics:

TUniqueList<T> = class(TList<T>)
public
  function Add(const Value: T): Integer;
end;

{ TUniqueList<T> }

function TUniqueList<T>.Add(const Value: T): Integer;
begin
  if not Contains(Value) then
    Result := inherited Add(Value);
end;

And if performance with lots of integers is important then you can keep the list sorted and use the binary serch

Answer 5

Delphi containers class in the "standard" VCL library are poor. This is a long standing issue only partially corrected in latest versions. If you are using Delphi >= 2009 you have generics class that can handle integer data types as well, before you have to write your own class, use TList in a non standard way, or use a third party library. If you have to store numbers, if they are at most 32 bit long you can store them in a TList, casting them to and from pointers. You have to override the Add() method to ensure uniqueness. You could also use TBits and set to true the corresponding "slot". Otherwise you need to use third party libraries like the JCL (free) or DIContainers (commercial), for example.

Answer 6

You can use a TList to store a set of integers. It is supposed to store Pointers, but since Pointers are just integers it works perfectly when storing Integers.

Answer 7

Delphi has unit mxarrays (Decision Cube), there is a class TIntArray, set it's property Duplicates to dupIgnore. It's also can sort values. If you will use it, see Quality Central Report #:2703 to correct the bug in this unit.

Answer 8

Personally, i strongly recommend start using DeCAL for storing data. It has DMap container which can handle almost any data type, is self optimized because it uses internal Red-Black tree and it won't allow you to add duplicates (if you need to insert duplicates, you can use DMultiMap). Another great thing with DMap is that finding element in the list is very fast (much faster than in TStringList). Working with DeCal is a bit different than with other Delphi libraries but once you get comfortable with it, you won't use any StringList in your code.

Edit: older version of DeCAL is on SourceForge, but here you can find great pdf manual.

Answer 9

Yes, there is, it's called TDictionary