Re: Object-relational impedence

"Marshall" <marshall.spight_at_gmail.com> wrote in message news:a8e31977-9f84-4c58-bca3-e0aa4e855676_at_s19g2000prg.googlegroups.com...
> On Mar 10, 5:30 am, "Yagotta B. Kidding" <y..._at_mymail.com> wrote:
> > Marshall <marshall.spi..._at_gmail.com> wrote
> > > On Mar 9, 7:25 pm, "Yagotta B. Kidding" <y..._at_mymail.com> wrote:
> >
> > >> Superficially, you can perform the translation, but the assignment
> > >> required to imitate the projection makes any such language not
> > >> referentially transparent. You may consider the non-transparency a
> > >> non- issue of course.
> >
> > > Um, how so? I'm not sure I see what you mean.
> >
> > "A language that supports the concept that ``equals can be substituted
> > for equals'' in an expresssion without changing the value of the
> > expression is said to be referentially transparent. Referential
> > transparency is violated when we include set! in our computer language.
> > This makes it tricky to determine when we can simplify expressions by
> > substituting equivalent expressions. Consequently, reasoning about
> > programs that use assignment becomes drastically more difficult."
>
> Dude? I'm a language junkie with an interest in FP. It wasn't the
> term "referential transparency" I was having trouble with. :-)
>
> Rather, I don't see where the assignment comes in. Particularly
> in discussing SQL, which, strictly speaking, lacks assignment.
> (Although it does have other imperative operators, yes.) And
> Mr. Perryman's example was written in a single-assignment,
> mathematical style.
>

Oh?

I thought that the SET clause of the UPDATE statement was an assignment in disguise.

> > http://mitpress.mit.edu/sicp/full-text/sicp/book/node54.html
>
> Ah, SICP. Did you know that David Cressey's name appears
> in it? Apparently he was at ground zero in the early days of
> garbage collection, and coined a term that is still used. I told
> that story when my languages discussion group had
> Mr. Abelson for lunch.
>
>
> Marshall
>
> PS. Name dropping alert!!! I try to resist, but I am weak.
Received on Mon Mar 10 2008 - 18:55:28 CET