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From: bdhelm@immd4.informatik.uni-erlangen.de (Bernd Helm)
Newsgroups: comp.lang.pascal
Subject: Re: TP6.0 OOP Quiery
Message-ID: <1991Jun17.120123.4946@informatik.uni-erlangen.de>
Date: 17 Jun 91 12:01:23 GMT
References: <1991Jun16.075044.18283@cs.mcgill.ca> <1991Jun17.005251.1184@maytag.waterloo.edu>
Organization: CSD., University of Erlangen, Germany
Lines: 38

dmurdoch@watstat.waterloo.edu (Duncan Murdoch) writes:

>In article <1991Jun16.075044.18283@cs.mcgill.ca> storm@cs.mcgill.ca (Marc WANDSCHNEIDER) writes:
>>
>>In the TP 6.0 Users manual, they start building up OOPs with objects typed
>>Location and Point.
>...
>>
>>MY problem is: Why have they declared an INIT procedure for type Point, when 
>>Location already has this procedure declared.  If objects have inheritance,
>>then there should already be an INIT procedure built into the Point type.

>In the example you gave, you are correct:  though declared as 
>constructors, the two Init routines are just procedures.  However, in more

I think, you missed the point: Point.Init is needed to initalize correctly
the Visible-variable in Point where Location.Init doesn't know anything
about Visible:

>>  Point = object(Location)
>>    Visible: Boolean;
      ^^^^^^^^
>>    procedure Init(InitX, InitY: integer);


I would implement Point.Init so:

    procedure Point.Init(InitX, InitY: integer);
    begin
	Location.Init(InitX, InitY);
	Visible := FALSE;
	{ do what is needed to show the point... }
    end;



bye,bye
	Bernd