Passing Static arrays as parameters for Dynamic arrays in Delphi

Question

Hi dudes,

I have this array:

const / var
  _Data : array [0..4] of array [0..3] of Double =
    ((0,0,0,0),
     (0,0,1,1),
     (1,0,1,0),
     (1,1,0,0),
     (1,1,1,1));

I wanna pass it as param value for this procedure:

procedure NN.NetTraining(Data: TDoubleMatrix);

Where:

  TDoubleArray    = array of Double;
  TDoubleMatrix   = array of TDoubleArray;

Is There some manner to cast or convert this static array into dynamic array in Delphi (2009) ?

Thanks in advance.

Answer 1

Dynamic arrays differ from normal arrays.

Dynamic arrays are pointers, while normal arrays are blocks of memory. With one dimensional arrays, you can use the address of the array. But with multi dimensional arrays this trick won't work.

In your case, I would use a file to initialize the array. So you can use dynamic arrays 100% of the time. Else you have to write your own conversion which kind of defeats the purpose of dymanic arrays.

Answer 2

May be you should use open arrays instead?

Answer 3

You can't cast but you can copy! Something like...

    procedure CopyDMatrix(var Source; LengthX, LengthY: integer; var Dest: TDoubleMatrix);
    const
      SizeOfDouble = SizeOf(Double);
    var
      n  : integer;
      ptr: pointer;
    begin
      SetLength(Dest, LengthX);
      Ptr := @Source;
      for n := 0 to LengthX - 1 do begin
        SetLength(Dest[n], LengthY);
        Move(ptr^, Dest[n][0] , SizeOfDouble * LengthY);
        inc(cardinal(ptr), SizeOfDouble * LengthY);
      end;
    end;

    //...  

    CopyDMatrix(Data, Length(Data), Length(Data[0]), DoubleMatrix);

Answer 4

Check here: http://chee-yang.blogspot.com/2008/10/delphi-2009-array-is-dead-long-live.html