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initialize a dynamic array

Posted on 2009-05-08
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Last Modified: 2012-05-06
I need many 2D Matrices in different dimensions.
I#m working with a dynamic array  2DMatrix_REAL;

How to initialize the dyn. array in an elegant way.

Current solution

      setlength(Amatrix, x,y)

      Amatrix[0,0] := .....     Amatrix[ ,] :=    .......

      takes millions of lines of code.!
      Can I copy the Static array Identity  to a Dynamic Array ?
Identity : array [1..5, 1..5] of Real  =
                         ((  0,    0,    0 , 0   , 0   ) ,
                          (  0 ,   0,    0 , 0   , 0   ) ,
                          (  0,    0,    1 , 0   , 0   ) ,
                          (  0 ,   0,    0 , 0   , 0   ) ,
                          (  0 ,   0,    0 , 0   , 0   ) );
 
 
 
type   2DMatrix_REAL =  array of array of Real;

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Question by:BdLm
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6 Comments
 
LVL 19

Accepted Solution

by:
MerijnB earned 2000 total points
ID: 24343709
you can iterate through it

var i, j: integer;
begin
 setlength(Amatrix, x,y)
 for i := 0 to x - 1 do
  for j := 0 to y - 1 do
   Amatrix[x, y] := 0;
end;

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LVL 31

Expert Comment

by:moorhouselondon
ID: 24344147
Couldn't you create a buffer that mapped over the array (using the Absolute directive), then initialise that in code?

From Delphi Help:-

Absolute Addresses
You can create a new variable that resides at the same address as another variable. To do so, put the directive absolute after the type name in the declaration of the new variable, followed by the name of an existing (previously declared) variable. For example,

var
   Str: string[32];
   StrLen: Byte absolute Str;
specifies that the variable StrLen should start at the same address as Str. Since the first byte of a short string contains the string's length, the value of StrLen is the length of Str.

You cannot initialize a variable in an absolute declaration or combine absolute with any other directives.

0
 
LVL 19

Expert Comment

by:MerijnB
ID: 24345132
You have to be careful with that since a dynamic array is actually a pointer.
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Author Comment

by:BdLm
ID: 24345417
any better solution than this one,

      TFilter3D = array [1..3,1..3] of Real;
      TFilter4D = array [1..4,1..4] of Real;
      TFilter5D = array [1..5,1..5] of Real;
      TFilter6D = array [1..6,1..6] of Real;
      TFilter7D = array [1..7,1..7] of Real;
 
 
const SampleFiler  : TFilter3D  =
                         ((  0 ,   0.2 , 0   ) ,
                          (  0.2,  0.2,  0.2 ) ,
                          (  0 ,   0.2 , 0   ));
 
 
 
 
 
 
 
//  copy static array to dyn. array  dim =6
procedure LoadDynArrayFromStaticArray ( aFilter :  TImageFilterReal;  Dim : Integer; aStaticArray : TFilter6D ); overload;
var  i,j   : Integer;
begin
      setlength(AFilter, dim,dim);
 
      for i := 0 to dim -1  do
        for j := 0 to dim-1 do
             aFilter[i,j] := aStaticArray[i+1,j+1];
 
end;
 
//  copy static array to dyn. array  dim =5
procedure LoadDynArrayFromStaticArray ( aFilter :  TImageFilterReal;  Dim : Integer; aStaticArray : TFilter5D ); overload;
var  i,j   : Integer;
begin
      setlength(AFilter, dim,dim);
 
      for i := 0 to dim -1  do
        for j := 0 to dim-1 do
             aFilter[i,j] := aStaticArray[i+1,j+1];
 
end;
 
//  copy static array to dyn. array  dim =4
procedure LoadDynArrayFromStaticArray ( aFilter :  TImageFilterReal;  Dim : Integer; aStaticArray : TFilter4D ); overload;
var  i,j   : Integer;
begin
      setlength(AFilter, dim,dim);
 
      for i := 0 to dim -1  do
        for j := 0 to dim-1 do
             aFilter[i,j] := aStaticArray[i+1,j+1];
 
end;
 
//  copy static array to dyn. array  dim =3
procedure LoadDynArrayFromStaticArray ( aFilter :  TImageFilterReal;  Dim : Integer; aStaticArray : TFilter3D ); overload;
var  i,j   : Integer;
begin
      setlength(AFilter, dim,dim);
 
      for i := 0 to dim -1  do
        for j := 0 to dim-1 do
             aFilter[i,j] := aStaticArray[i+1,j+1];
 
end;
 
 
 
procedure LoadImageFilterByIndex( aFilterNameIndex : integer;  var  aFilter : TImageFilterReal);
var  i ,j :  Integer;
begin
        case aFilterNameIndex  of
 
        0:   LoadDynArrayFromStaticArray ( aFilter, 3 , BasicBlur );
 
        1:    begin
 
              end;
        2:    begin
 
              end;
        3:    begin
 
 
              end;
 
        else
 
 
        end;
 
 
 
end;

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LVL 14

Expert Comment

by:Pierre Cornelius
ID: 24351670
Easiest way is to simply copy the data using move function. see sample:
unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;
 
 
type
  T2dMatrix_REAL = array[1..5, 1..5] of real;
  T2DMatrix_Rec = record
    Description: string;
    Matrix: T2DMatrix_REAL;
  end;
  TMatrices = array of T2dMatrix_Rec;
 
const
 
  Identity : T2dMatrix_REAL  =
                         ((  1,    2,    3 , 4   , 5   ) ,
                          (  6 ,   7,    8 , 0   , 10  ) ,
                          (  11,   12,   13, 14  , 15  ) ,
                          (  0 ,   0,    0 , 0   , 0   ) ,
                          (  0 ,   0,    0 , 0   , 0   ) );
 
 
 
 
 
type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    Matrices: TMatrices;
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.Button1Click(Sender: TObject);
var c: char;
    i: integer;
begin
  SetLength(Matrices, 10);
  for c:= 'A' to 'J' do
  begin
    i:= Ord(c) - Ord('A');
    Matrices[i].Description:= c+c+c+c+c;
    move(identity[1,1], matrices[i].Matrix[1,1], SizeOf(T2dMatrix_REAL));
  end;
  if (Matrices[1].Matrix[1,1] = 0) then;
end;
 
end.

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LVL 8

Author Closing Comment

by:BdLm
ID: 31579646
may be Delphi does not offer any more compact solution
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