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Re: What databases have taught me

From: Dmitry A. Kazakov <mailbox_at_dmitry-kazakov.de>
Date: Fri, 30 Jun 2006 19:08:30 +0200
Message-ID: <1mxnfautmh7v1.1d3i3v6nossc5.dlg@40tude.net>


On 30 Jun 2006 09:39:29 -0700, Marshall wrote:

> Dmitry A. Kazakov wrote:

>> On 30 Jun 2006 08:39:09 -0700, Marshall wrote:
>>>>
>>>> Side note: in a strongly typed language "extension" of an operation can be
>>>> accomplished only through an "extension" of the type (actually a class of).
>>>> This happens by adding a new type to the class, so that the operation
>>>> extension be defined on that new type.
>>>
>>> I believe you are descring OO here, yes?
>>
>> Actually any typed system with user-defined relations on types, I don't
>> think that it is any specific to OO. Nothing prevents RM from allowing
>> polymorphic values in tuples. Also tuples themselves could be made
>> polymorphic as well (to support mixed logics, for example, or to attach
>> some constraints etc).

>
> Mmmm, what I was trying to point out is that it is a somewhat
> OOish idea to consider functions on a type as part of the
> definition of that type.
>
> Given a set A, and a set B.
> Given a function f: A -> B
>
> We would not *necessarily* consider f as part of the definition of A.

Absolutely. f is a part of definition of both.

type <-> function is a relation. "Member" function is rubbish. BTW, when I talk about multiple dispatch I do include results of functions. So, say

+ : A x B -> C

is triple dispatching. It is an operation of types A, B, C.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
Received on Fri Jun 30 2006 - 12:08:30 CDT

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