Re: what are keys and surrogates?
Date: Fri, 18 Jan 2008 11:55:31 -0400
Message-ID: <4790cbf7$0$4043$9a566e8b_at_news.aliant.net>
Jan Hidders wrote:
> On 18 jan, 00:55, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
>>Jan Hidders wrote:
>>
>>>On Jan 17, 10:29 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>>
>>>>Jan Hidders wrote:
>>
>>>>>On 17 jan, 14:40, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>>
>>>>>>Marshall wrote:
>>
>>>>>>>On Jan 10, 7:07 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>>
>>>>>>>>Marshall wrote:
>>
>>>>>>>>>>Is "constructor" the same as what C. Date calls a "selector"?
>>
>>>>>>>>>Yes. Date calls it a selector, and the entire rest of the world
>>>>>>>>>calls it a constructor. :-)
>>
>>>>>>>>Except "selector" has no concept of physically building anything in storage.
>>
>>>>>>>Okay. Just specifying a value, or a kind of value, yes?
>>>>>>>That's more or less what I understand the most general
>>>>>>>definition of the word "constructor" to mean. The OOP
>>>>>>>world uses it a bit more specifically.
>>
>>>>>>I suspect the word originates in the OOP world, and it strongly suggests
>>>>>>building something physical.
>>
>>>>>>>>>I have no strong feelings about encapsulated ADTs; what
>>>>>>>>>Date calls ... uh. Shit. I can't remember what he calls them.
>>>>>>>>>I don't entirely see the reason for them. Performance I guess?
>>
>>>>>>>>Types? Possible representations? Type generators? Only the first is an
>>>>>>>>ADT, but I am curious whether you meant one of the others.
>>
>>>>>>>Possreps! That's the one!
>>
>>>>>>Having multiple possible representations for the same type allows data
>>>>>>independence--especially physical independence.
>>
>>>>>You think the number of possible representations and the number of
>>>>>possible ways to store something in memory or on disk are related?
>>>>>Why?
>>
>>>>The latter grows linearly with the former.
>>
>>>Why? Seriously. Why do you think there is a relationship at all? Why
>>>would the number of ways a value can be represented to the user
>>>(something which a matter of definition and/or convention) have any
>>>bearing on how many ways there are to map it to 1's and 0's?
>>
>>Why do you think representations are limited to representing to users?
> > I don't. I think possreps are. But I could be wrong about their > definition.
I strongly suspect you are.
So what is exactly a possrep according to you? Are you > saying that the number of possreps of a certain value is by definition > the number of ways it can be represented as ... as what?
I don't understand the part starting with "as". I would punctuate the sentence there instead.
>>How does representing to a user differ from representing to a machine?
>
> You don't get out much, do you? :-)
That kind of man-machine interface never even occured to me. One wonders what causes your mind to wander in that direction. Received on Fri Jan 18 2008 - 16:55:31 CET