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From: Maciej Sobczak <no.spam@no.spam.com>
Newsgroups: comp.lang.ada
Subject: Re: Dynamically tagged expression required
Date: Mon, 12 Dec 2005 10:44:22 +0100
Organization: CERN - European Laboratory for Particle Physics
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Date: 2005-12-12T10:44:22+01:00
List-Id: <comp.lang.ada>

Martin Krischik wrote:

>>OK, so that explains why it's possible to use Shape'Class as a parameter
>>in subroutine. Every time the subroutine is called, the parameter is
>>*initialized* with the value, and therefore it can be different for each
>>call:
>>
>>procedure Draw(S : Shape'Class);
> 
> You know this procedure won't dispatch?

Yes, I want to dispatch *inside* it. I treat it as a more or less 
equivalent to this in C++:

void draw(Shape const &s);

(by more or less equivalent I mean that I'm likely to use them in the 
same design situations, not that they produce the same machine code, 
even if they do)


>>T : Triangle;
>>R : Rectangle;
>>
>>and later:
>>
>>Draw(T);   -- S initialized with T
>>Draw(R);   -- S initialized with R
>>
>>Right?
> 
> Yes. But it only look like the parameter is initialized. Internally the
> compiler likely to use a pointer to pass the paramer to speed up things.

I don't care. :)
I don't want to call something a "pointer" when it isn't in my program.

 > Remember "in" parameter are also constant.

Yes.

> Once the variable is initialized it becomes constained - you can only
> assigned object of the same constain to them.
> 
> Simpler example:
> 
> declare
>   Text : String := "Hello"; - (A)
> begin
>  Text := "World"  - (B)
>  Text := "World!" - (C)
> end

It makes sense now.
Thank you for all the responses,


-- 
Maciej Sobczak : http://www.msobczak.com/
Programming    : http://www.msobczak.com/prog/