variable size arrays

Posted on 1998-06-03
Last Modified: 2010-04-06
In my program I am using an array[0..9,0..9] of Extended. But I would like to have the user to determine the size of the array, instead of pre-defining it.
It doesn't have to be an array. It can be a pointer or something that can be accessed as a bi-dimensional array, but with the size determined at run-time.
Question by:acerola
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Author Comment

ID: 1350133
I tried that solution. It locked my machine. Than I took that idea, but used GetMem instead of that weird memory allocation procedure. It worked, but the program itself didn't. When I used an array larger than 4x4 the calculation result was always zero. Maybe it's because my program calls a function recursively.

Does anyone have any other suggestion?

Raised the points to 50.

Expert Comment

ID: 1350134
use variant type
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Author Comment

ID: 1350135
This answer is way too generic. Be more specific (e.g. give me an source code). Just changing the variable type from extended to variant will not solve the problem.

Accepted Solution

descikartus earned 50 total points
ID: 1350136
Try the following code:

program Project1;

  SysUtils, Dialogs;

{$R *.RES}

  PDouble = ^Double;

// This will get a value from the array.
// All you have to do is pass the array, the width of
// the array, and the location within it that you want.
// This function assumes a two dimentional array, modify
// at will.
function GetDouble(const AD : array of Double; W, X, Y : Integer) : Double;
  Result := AD[Y * W + X];

// This works similar to the function above, except
// you are also passing it a value.
procedure SetDouble(PD : PDouble; W, X, Y : Integer; Value : Double);
      Integer(PD) +
      (Y * W * SizeOf(Double) + X * SizeOf(Double))
    )^ := Value;

// Just some variable to show you how it works
  PADouble : PDouble;
  W, H : Integer;
  DoubleVar : Double;


  // Set up our dynamic array
  W := 9;
  H := 9;
  GetMem(PADouble, H * W * SizeOf(Double));

  // Assign a value within it
  SetDouble(PADouble, W, 5, 5, 3.14159265);

  // Get the value back
  DoubleVar := GetDouble(PADouble^, W, 5, 5);

  // Display our value


Hopefully this helps.


Author Comment

ID: 1350137
Works just perfectly.

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