Re: what are keys and surrogates?
Date: Sun, 27 Jan 2008 22:09:57 -0400
Message-ID: <479d397c$0$4076$9a566e8b_at_news.aliant.net>
Marshall wrote:
> 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.
In my mind, the canonical example is the Complex data type. Phasors/polars are faster to multiply and cartesians are faster to add. I should expect one would want to choose whether to physically store Complex values as phasors as cartesian coordinates or as a tagged representation that could be either.
> 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.
Like many programmers, I suspect your experience relies less on abstract data types and more on algorithms. Received on Mon Jan 28 2008 - 03:09:57 CET