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From: Martin Dowie <martin.dowie@btopenworld.com>
Newsgroups: comp.lang.ada
Subject: Re: Base'Class is instance of Der1?
Date: Sat, 8 Jan 2005 14:25:43 +0000 (UTC)
Organization: BT Openworld
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Date: 2005-01-08T14:25:43+00:00
List-Id: <comp.lang.ada>

Martin Krischik wrote:
> Hi R
> 
> R wrote:
> 
> 
>>Hello.
>>
>>I've got function which has a parameter of type Base'Class.
>>
>>well I have 3 derived tagged records and depending of what exactly is
>>the parameter I have to cast it to a proper function.
> 
> 
> Maybe you want a view rename instead of a cast:
> 
> http://en.wikibooks.org/wiki/Programming:Ada:Subtypes#Rename_View

Surely:

type Parent_Type is tagged null record;
type Child_Type is tagged null record;

Child_Instance : Child_Type;
Parent_View : Parent_Type'Class renames Parent_Type'Class (Child_Type);

Should be:

type Parent_Type is tagged null record;
type Child_Type is new Parent_Type with null record;

Child_Instance : Child_Type;
Parent_View : Parent_Type'Class renames Parent_Type'Class (Child_Instance);


Cheers

-- Martin