From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,86a457a80a9f4412
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!postnews.google.com!e51g2000hsg.googlegroups.com!not-for-mail
From: andrew <andrew.carroll@okstate.edu>
Newsgroups: comp.lang.ada
Subject: Re: Generic Collection
Date: 8 May 2007 14:59:46 -0700
Organization: http://groups.google.com
Message-ID: <1178661586.585164.191690@e51g2000hsg.googlegroups.com>
References: <1178652593.006083.173150@l77g2000hsb.googlegroups.com>
   <1178658022.9164.17.camel@kartoffel>
NNTP-Posting-Host: 139.78.128.110
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
X-Trace: posting.google.com 1178661587 8763 127.0.0.1 (8 May 2007 21:59:47
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Tue, 8 May 2007 21:59:47 +0000 (UTC)
In-Reply-To: <1178658022.9164.17.camel@kartoffel>
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1;
 InfoPath.1; .NET CLR 1.1.4322),gzip(gfe),gzip(gfe)
Complaints-To: groups-abuse@google.com
Injection-Info: e51g2000hsg.googlegroups.com; posting-host=139.78.128.110;
   posting-account=Kq9unQ0AAADh_grEViI3JGqegXKDDjxt
Xref: g2news1.google.com comp.lang.ada:15666
Date: 2007-05-08T14:59:46-07:00
List-Id: <comp.lang.ada>

On May 8, 4:00 pm, Georg Bauhaus <rm.tsoh+bauh...@maps.futureapps.de>
wrote:
> On Tue, 2007-05-08 at 12:29 -0700, andrew wrote:
> > I cannot say for sure if the "is a" relations aren't entirely
> > artificial.  It seems to me it would work either way.  The difference
> > for me is that I cannot visualize the composition you mentioned.
>
> As you noted, I meant that "a tuple is a collection of attributes"
> doesn't necessarily imply inheritance relationship; TUPLE doesn't have
> to inherit from a type COLLECTION_OF_ATTRIBUTES.
>
> I think there are various possibilities; RDB2 (below RDB) shows
> types that have components of other types (that is, are composed :-)
> but are otherwise unrelated.
> Package RDB desclares "is a" relations in the sense you describe
> by making the DB types be "a collection of" objects of "smaller"
> types.
>
> > So what you are saying is that the type Item in my example is the
> > parameter you are talking about?
>
> Erh, I guess so.
>
> with Ada.Containers.Hashed_Sets;
> with Data;
>
> package RDB is
>
>    use Ada;
>
>    type DP is access Data.T'class;
>    function compare(a, b: DP) return BOOLEAN;
>    function hash(element: DP) return Containers.HASH_TYPE;
>
>    subtype ATTRIBUTE is DP;
>
>    package Attributes is new Containers.Hashed_Sets
>      (ELEMENT_TYPE => ATTRIBUTE,
>       hash => hash,
>       equivalent_elements => compare);
>
>    subtype TUPLE is Attributes.SET;
>    function hash(element: TUPLE) return Containers.HASH_TYPE;
>
>    package Tuples is new Containers.Hashed_Sets
>      (ELEMENT_TYPE => TUPLE,
>       hash => hash,
>       equivalent_elements => Attributes."=",
>       "=" => Attributes."=");
>
>    subtype TABLE is Tuples.SET;
>    function hash(element: TABLE) return Containers.HASH_TYPE;
>
>    package Tables is new Containers.Hashed_Sets
>      (ELEMENT_TYPE => TABLE,
>       Hash => hash,
>       equivalent_elements => Tuples."=",
>       "=" => Tuples."=");
>
>    -- ...
>
> end RDB;
>
> with Ada.Containers.Hashed_Sets;
> with Data;
>
> package RDB2 is
>
>    use Ada;
>
>    type DP is access Data.T'class;
>    function compare(a, b: DP) return BOOLEAN;
>    function hash(element: DP) return Containers.HASH_TYPE;
>
>    subtype ATTRIBUTE is DP;
>
>    package Attributes is new Containers.Hashed_Sets
>      (ELEMENT_TYPE => ATTRIBUTE,
>       hash => hash,
>       equivalent_elements => compare);
>
>    type TUPLE is
>       record
>          -- ...
>          columns: Attributes.SET;
>       end record;
>    function compare(a, b: TUPLE) return BOOLEAN;
>    function hash(element: TUPLE) return Containers.HASH_TYPE;
>
>    package Tuples is new Containers.Hashed_Sets
>      (ELEMENT_TYPE => TUPLE,
>       hash => hash,
>       equivalent_elements => compare);
>
>    type TABLE is
>       record
>          -- ...
>          rows: Tuples.SET;
>       end record;
>    function compare(a, b: TABLE) return BOOLEAN;
>    function hash(element: TABLE) return Containers.HASH_TYPE;
>
>    package Tables is new Containers.Hashed_Sets
>      (ELEMENT_TYPE => TABLE,
>       Hash => hash,
>       equivalent_elements => compare);
>
>    type SCHEMA is
>       record
>          -- ...
>          relations: Tables.SET;
>       end record;
>
> end RDB2;

RDB2 looks good to me and is pretty close to what I had in mind.

I think I finally get what you were saying about inheritance.  Before
I posted the topic I was thinking about the design and I just wrote
down the "table is a collection" as part of sentence.  In my mind I
was thinking of a variable declaration:

table: collection;
tuple: collection;
schema: collection;

and so I posted my question.