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initialize a dynamic array

Posted on 2009-05-08
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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;
``````
0
Question by:BdLm

LVL 19

Accepted Solution

MerijnB earned 500 total points
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;
``````
0

LVL 31

Expert Comment

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

From Delphi Help:-

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

You have to be careful with that since a dynamic array is actually a pointer.
0

LVL 8

Author Comment

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;
``````
0

LVL 14

Expert Comment

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.
``````
0

LVL 8

Author Closing Comment

may be Delphi does not offer any more compact solution
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