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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: If not Ada, what else...
Date: Wed, 22 Jul 2015 12:27:03 +0200
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Xref: news.eternal-september.org comp.lang.ada:26971
Date: 2015-07-22T12:27:03+02:00
List-Id: <comp.lang.ada>

On Wed, 22 Jul 2015 11:05:23 +0200, Mart van de Wege wrote:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
> 
>> On Tue, 21 Jul 2015 15:55:26 -0700, Jeffrey R. Carter wrote:
>>
>>> On 07/21/2015 02:51 PM, Dmitry A. Kazakov wrote:
>>>> On Tue, 21 Jul 2015 22:06:54 +0100, Simon Wright wrote:
>>>> 
>>>>> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
>>>>>>
>>>>>> Operations do not belong to types.
>>>>>
>>>>> Huh?
>>>> 
>>>> function "*" (X : Matrix; Y : Vector) return Vector;
>>>> 
>>>> To which type does "*" belong?
>>> 
>>> A concept of programming by extension is that operations on extensible types do
>>> belong to a type.
>>
>> Why?
>>
>> Anyway, that does not answer the question. To which type belongs
>> multiplication?
> 
> I'd say it's a multimethod, being dispatched on all its parameters, not
> a member of a type.

A full dispatch, assuming Matrix and Vector unrelated.

Multimethod is a full dispatch with all arguments and the result restricted
to the same types hierarchy, e.g.

   function "*" (Left, Right : Matrix) return Matrix;

E.g.

   X : Sparse_Matrix;
   Y : Band_Matrix;
   Z : Dense_Matrix;
   
   Z := X * Y;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de