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From: lutz@iks-jena.de (Lutz Donnerhacke)
Newsgroups: comp.lang.ada
Subject: Re: Ada 200X Assertions
Date: Wed, 5 Dec 2001 19:36:01 +0000 (UTC)
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* Matthew Heaney wrote:
>"Lutz Donnerhacke" <lutz@iks-jena.de> wrote in message
>> Typical example 2: A head node of a linked list contains a next pointer
>>     which should be handled exactly as the next pointer of the real
>>     list nodes, but no payload at all.
>
>In the code below, I do this by making the List_Type a private derivation of
>a Node_Type. Which means a List_Type, containing only the head pointer, can
>be used exactly like Node_Type.

>   type Node_Type is abstract tagged private;
>   type List_Type is new Node_Type with private;

That's not a generic mixin.

My job is:
  task type Bla is ...;
  type Blas is array (Positive range <>) of Bla;
  type Foo (len : Natural) is abstract record
    t : Bla (Positive'First .. len);
  end record;
  procedure Process (a : Foo) is abstract;
  
  package Bla_List is new List (Bla);
  package Bla_List2 is new List (Bla);

In short: I'm looking for a extension of existing types to well known data
structures.

>> >Of course the language already allows you to move from a pointer to
>> >component to a pointer to aggregate: just use an access discriminant.
>>
>> This generates a completely different structure.
>
>What's wrong with that?

The memory layout shared by some hardware.

Thanx for your non generic examples.