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From: =?iso-8859-15?Q?Yannick_Duch=EAne_=28Hibou57=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Generic operation and prefixed notation
Date: Mon, 14 Jun 2010 20:11:13 +0200
Organization: Ada At Home
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Date: 2010-06-14T20:11:13+02:00
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Le Mon, 14 Jun 2010 19:47:09 +0200, Marek Janukowicz  =

<marek@janukowicz.net> a =E9crit:

Hi Marek,

> Given a simplified example:
>
>   type Model is tagged record
>     null
>   end record;
>
>   generic
>     Attr_Name : String;
>   procedure Get_Attribute( M : Model );
Here, Get_Attribute is not a primitive operation of Model I suppose.
If it is not a primitive operation of Model, you cannot invok it using t=
he  =

dotted notation.

For a subprogram to be a primitive, it must be declared in the same  =

package as the one which declares the type (here Modem). That is OK here=
  =

for that. However, it also additionally requires the type is not frozen.=
  =

Here, when you define a generic using a Model as an argument, I'm pretty=
  =

sure this makes Model frozen.

Basically, a type is made frozen as soon as some reference to it require=
s  =

some important stuff are already defined. When you make some kind of  =

reference to a type, it suppose the type is frozen, that is, all these  =

important stuff are already defined.

Hint (as kind of personal opinion): I prefer to restrict to dotted  =

notation to access record fields in implementation, and just use the  =

classic subprogram invocation even with tagged. However, this is not  =

always handy with inherited operation.

-- =

There is even better than a pragma Assert: a SPARK --# check.
--# check C and WhoKnowWhat and YouKnowWho;
--# assert Ada;
--  i.e. forget about previous premises which leads to conclusion
--  and start with new conclusion as premise.