Re: what are keys and surrogates?

On Jan 17, 5:40 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> Marshall wrote:
>
> >>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.

They use the word in the FP world too, and they hate those OOP guys probably more than we do! :-) :-) :-)

> >>>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.

Right. It's just that I can't seem to fit the need for physical independence
at the scalar type level into my brain. It may well be a bug in my thought
process. I don't *reject* the idea but I don't *accept* it either. I just
can't get any mental traction on it at all.

It would probably help if I had a use-case that matches something from my own experience. The usual examples don't solve any problems I can recall having. Could just be that I haven't been in the situation where the idea is useful.

Marshall Received on Thu Jan 17 2008 - 17:45:20 CET