Jeremy Nixon am Dienstag, 15. November 2005 23.16:
> John Doe <[EMAIL PROTECTED]> wrote:
> > Hope it's not a stupid question, but are you sure %d_cache survives a
> > request? Maybe I'm totally misunderstanding something but I thought
> > after the point
> >
> > } end lexical scope
> >
> > %d_cache gets destroyed (if not still referenced from somewhere else).
Jeremy, all, thanks very much for the replies; I really appreciate it,
especially since the questions _were_ stupid.
But nonetheless, it cleared some of my confusion (I think).
It seems that I use closure features from time to time, and from time to time
I'm totally confused about it.
> Lexical scope means the scope in which the "thing" is defined in the
> source. So, as far as the handler subroutine is concerned, the %d_cache
> variable never goes out of scope, and is never destroyed. It makes the
> subroutine into a closure, as someone else pointed out, though it's a
> different usage than you normally see for closures so I didn't think of
> that term to describe it.
Yes :-)
After all the replies I visualize the issue with 3 snippets:
my %d;
sub a { $d{a}++} }
{
my %d;
sub a { $d{a}++} }
}
sub b {
my %d;
return sub a { $d{a}++} }
}
> > I would have left out the scope-{} to keep %d_cache at file level.
> > Would that be wrong? And why?
>
> If you put it at the file level it is visible to the entire file. This
> probably won't hurt, but it is best in general to keep variable scope
> as limited as possible; in this case, it is visible where it is used,
> but not elsewhere.
>
> > Whereas something like
> >
> > $keep_ref=\%d_cache;
> >
> > in the handler() would, right?
>
> No, "reference" doesn't mean a literal reference, it's used in the English
> sense of simply referring to the variable in the source code.
This hint to the different meanings of 'reference' was very helpful!
Again, thanks a lot to all...
(And: modperl is great! As are all people working on it!)
