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From: Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>
Newsgroups: comp.lang.ada
Subject: Re: newbie - OOP in Ada Set and Get Methods
Date: Wed, 29 Dec 2004 17:35:20 +0000 (UTC)
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Date: 2004-12-29T17:35:20+00:00
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R <ruthless@poczta.onet.pl> wrote:
: 
: 'in parameters cannot be modified inside function'(sth like this),

This helps you abide by a principle called query command separation:

: procedure Set(this: in out rec1; s: Integer) is

this is the command, and the Get function is the query.
the principle says that queries should never modify the object.
Commands do in general modify the object.

(You can still implement a query using a procedure that has
an out parameter.)


-- Georg