Path: utzoo!attcan!uunet!munnari.oz.au!bunyip!brolga!uqcspe!batserver.cs.uq.oz.au!iain
From: iain@batserver.cs.uq.oz.au (Iain Fogg)
Newsgroups: comp.lang.pascal
Subject: Re: Dynamic arrays in TP5.0
Message-ID: <4219@uqcspe.cs.uq.oz.au>
Date: 10 Jul 90 00:29:58 GMT
References: <1831@krafla.rhi.hi.is>
Sender: news@uqcspe.cs.uq.oz.au
Reply-To: iain@batserver.cs.uq.oz.au
Lines: 47

binni@rhi.hi.is (Brynjolfur Thorsson) writes:

>Hi there.

>I am trying to use dynamic arrays in my TP5.0 program but am having a hard
>time. I want to be able to do things like they are done in C, e.g.

>*(x + 10) = 100.5

>but I have not found a way to do it. Below is a short program demonstrating
>what I want to do, but I have no idea, how to make GetVal and PutVal. If you
>have suggestions for me I would appreciate it. I can't believe that this is
>impossible in TP.

>***************************************************
>Program dynamic;

>Var
>   y : ^Real;
>   x : Real;

>Begin
>   GetMem(y, 10 * SizeOf(Real));
>   PutVal(y, 5, 12.34);
>   x := GetVal(y, 3);
>End.
>**************************************************

Try the following. Can't guarantee it's perfectly correct (haven't got
TP at work), but the idea's right. Obviously, there isn't any range
checking.

  TYPE
    RealPtr = ^Real;

  PROCEDURE PutVal (r_array: RealPtr; pos: Integer; value: Real);
  BEGIN
    r_array := RealPtr (longint (r_array) + (pos - 1) * SizeOf (Real));
    r_array^ := value
  END;
  
  FUNCTION GetVal (r_array: RealPtr; pos: Integer): Real;
  BEGIN
    GetVal := RealPtr (longint (r_array) + (pos - 1) * SizeOf (Real))^
  END;

Hope it helps, Iain.