Array begin from 0 or 1 in Delphi 5.0 Pascal?

Question

I want to do an ArrayList in Delphi 5.0. So I found a solution doing this code:

var arr: array of String;

OK, but every time I add something I do this:

var
    Form1: TForm1;
    var arr : array of String;

procedure TForm1.Button1Click(Sender: TObject);
var aux :string;
var len:integer;
begin
    len := Length(arr) + 1;
    SetLength(arr, len);
    arr[len-1] := 'abc' + IntToStr(len);
    Button1.Caption := arr[len-1]; // just to writeout something
end;

I'm a C++ programmer, and I do not know anything about Pascal. I always heard a Pascal index begins from 1, not 0. As in the above procedure I do arr[len-1] because of 0 index begin.

Is there a better way than Pascal arrays? Like with C++'s std::vector?

Answer 1

Dynamic arrays' indexes begin with zero

var
  a: array of Integer;
begin
  SetLength(a, 500);
  a[0] := 0;

Static arrays can have arbitrary indexes

var
  i: Integer;
  b: array [50..100] of Integer;
  c: array[-10..10] of Integer; 
begin
  for i := 50 to 100 do b[i] := i * i;

  // Note negative starting index above in declaration
  for i := -10 to 10 do c[i] := i * i;

Strings' indexes begin with one

var
  c: String;
begin
  c := 'Zap!';
  c[1] := 'W';
  ShowMessage(c); /// shows 'Wap!'

Anyway you can always use Low() and High() functions which return the lower and higher index of an array.

For handling a list of strings the most commonly used class is TStringList which is found in unit Classes.

Answer 2

What you're using is known as a dynamic array which is different from a Pascal classic array. Dynamic arrays are variable in size and the index is 0 based.

Classic Pascal arrays are not 0 nor 1 based... It's up to the programmer where the index start or ends. The only compiler restriction is that the index must be an ordinal type. You can declare

procedure x;
    var
        IntArr: array[50..75] of Integer;
        StrArr: array[0..49] of string;
        DblArr: array[1..10] of Double;