Re: Sets and Lists, again

David Cressey wrote:
> "dawn" <dawnwolthuis_at_gmail.com> wrote in message
> news:1148132310.308203.133240_at_g10g2000cwb.googlegroups.com...
> > David Cressey wrote:
> > > What's a ripple delete? How is it different from an ordinary delete?
> >
> >
> http://www.tincat-group.com/mewsings/2006/01/who-ordered-ripple-delete.html
> >
>
> Can you summarize this?

I was hoping the first few sentences did that, sorry. It is a delete that also renumbers or moves up subsequent data. In the case of a desired alpha ordering, this is simply a delete. In the case of a list or a numbered 1,2...n set (the number being an attribute in a relation, for example), removing the 3rd and 4th elements requires renumbering all of those after it.

> > > If you have sets, why would you have to "insert at this point"?

In the case of sets that are numbered as above, inserting a new 5th element requires that 6...n be renumbered. Have you ever seen the design often used with "relational databases" where you leave a range of 10 or n numbers on either side of numbered items so that you can stick new ones in up to the number of spots reserved? You don't need to design that way if using a list where the numbering is behind the scenes because the structure is a logical list.

> [no reply]
>
> Again, what does "insert at this point" buy you that insertion into a set
> doesn't buy you?
>
>
> > > Why do you need lists for this purpose?
> >
> > ? Why do you need lists for the purpose of having list operators? Can
> > you rephrase?
>
> Sure:
>
> What can you do with lists and list operators that you can't do with sets
> and set operators?

That is similar to "What can you do with a high level language that you could not do with assembler?" Ease of development and maintenance (aka cost savings). --dawn Received on Sun May 21 2006 - 00:56:34 CEST