NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/lang/pascal/6654

Text File | 1992-11-17 | 1.9 KB | 51 lines

Newsgroups: comp.lang.pascal
Path: sparky!uunet!utcsri!torn!news.ccs.queensu.ca!mast.queensu.ca!dmurdoch
From: [e-mail] (Duncan Murdoch)
Subject: Re: BP/TP OOP is missing something...
Message-ID: <[e-mail]>
Lines: 39
Sender: [e-mail] (Netnews control)
Organization: Queen's University
References: <[e-mail]> <[e-mail]>
Date: Tue, 17 Nov 1992 17:10:56 GMT

In article <[e-mail]> [e-mail] (Harry Kooijman,Peyt314a,3808) writes:
>Why is it that TP with objects does not have the capability to call the
>constructors when variables are declared? And when an object goes out of
>scope it should be destructed automatically. For example:
>
>Function DoSomethingWithD;
>Var D:DoubleObject(1.2);
>Begin
>  ...
>  Do something with D
>  ...
>End; {and here D gets destructed}

This is there in TP, to a very limited extent:  you can have an initialized
variable which is an object, and you needn't call the constructor.  It's
initialized at program load time, not each time the variable comes into
scope.  The destructor is never called.

I think the main reason that TP doesn't have automatic constructor/
destructor calls is because it is descended from Pascal.  In Pascal in
general, code doesn't get executed unless you explicitly ask for it.
Adding automatic code would be a big change to the flavour of the language.

It's pretty unlikely that Borland would make such a fundamental change
that doesn't add any power to the language.  Your code fragment is exactly
equivalent to

 var D:DoubleObject;
 begin
   D.init(1.2);
   ...
   D.done;
 end;

Since what you want to do is already possible with nothing more than a
couple of extra lines of code, why make a big change to the language?

Duncan Murdoch
[e-mail]