Delphi re-indexes arrays passed to functions?

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Hi all,

I don't use Delphi often so this is probably a stupid question again, but why does Delphi (7) re-index arrays when they're passed to a function, as a simplified example...

Pascal and Delphi Syntax (Toggle Plain Text)
program example;
{$APPTYPE CONSOLE}
uses
  SysUtils;
var
  numbers: array[1..5] of Integer = (10, 20, 30, 40, 50);
 
procedure example(var nums: array of Integer);
begin
  WriteLn(nums[5]); //Undefined. 50 -> nums[4]
end;
 
begin
  Writeln(numbers[5]);
  example(numbers);
  Readln;
end.
program example;
{$APPTYPE CONSOLE}
uses
  SysUtils;
var
  numbers: array[1..5] of Integer = (10, 20, 30, 40, 50);

procedure example(var nums: array of Integer);
begin
  WriteLn(nums[5]); //Undefined. 50 -> nums[4]
end;

begin
  Writeln(numbers[5]);
  example(numbers);
  Readln;
end.

Why does it do this? Thanks in advance for any answers.

Last edited by TomRandall; Sep 27th, 2009 at 2:59 pm.

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TomRandall

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Sep 28th, 2009

Re: Delphi re-indexes arrays passed to functions?

Hello
this happend because an array index in Pascal by default start from 0
your array in Main program Start From 1 But the array that is defined in procedure is started from 0 By Default
so if you want to print fifth element of array in procedure you mast print num[4] in procedure.

fayyaz

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since Jun 2007

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Sep 28th, 2009

Re: Delphi re-indexes arrays passed to functions?

What if the added parameter type is not meet properly?
Listen,if you create a new type as array and pass it to the proc...

delphi Syntax (Toggle Plain Text)
 
program array1___;
{$APPTYPE CONSOLE}
uses
  SysUtils;
 
type TArray = array[1..5]of integer;
 
const numbers:TArray = (10,20,30,40,50);
 
 
procedure example(const nums: TArray);
begin
  WriteLn(nums[5]);
end;
 
begin
  Writeln(numbers[5]);{result is 50}
  example(numbers);{here too}
  Readln;
end.
program array1___;
{$APPTYPE CONSOLE}
uses
  SysUtils;

type TArray = array[1..5]of integer;

const numbers:TArray = (10,20,30,40,50);


procedure example(const nums: TArray);
begin
  WriteLn(nums[5]);
end;

begin
  Writeln(numbers[5]);{result is 50}
  example(numbers);{here too}
  Readln;
end.

FlamingClaw

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since Feb 2009

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