I was thinking about regular expressions and hypotheticals again this
weekend, and something was bothering me quite a lot. How do rules create
hypotheticals?
Since a rule behaves like a closure, I can see how it could gain access
to existing lexicals, if it's declared inside of the same scope:
> Going back to patterns, this gives us an added bonus. It not only
> explains the behavior of hypotheticals, but also of subexpression
> placeholders, which are created when the pattern returns:
>
> $self but lexicals(0=>$self, 1=> $self.{1}, 2=> $self.{2}, etc...)
>
> That yields the
I may be missing your point, but based on my somewhat
fuzzy understanding:
> Oh. Duh. Why don't we have such a mechanism for matches?
>
> m/ my $date := /
>
> is ambiguous to the eyes. But I think it's necessary to have a
lexical
> scoping mechanism for matches
The above would at least hav
On Mon, Sep 09, 2002 at 02:14:25PM -0500, Me wrote:
> Hence the introduction of let:
>
> m/ { let $date := } /
>
> which makes (a symbol table like entry for) $date available
> somewhere via the match object.
Somewhere? where it appears in in the namespace of the caller.
Apparently there
On Mon, 9 Sep 2002, Andrew Wilson wrote:
> On Mon, Sep 09, 2002 at 02:14:25PM -0500, Me wrote:
> > Hence the introduction of let:
> >
> > m/ { let $date := } /
> >
> > which makes (a symbol table like entry for) $date available
> > somewhere via the match object.
>
> Somewhere? where it
On Mon, Sep 09, 2002 at 02:13:55PM -0600, Luke Palmer wrote:
> Err.. I don't think so.
>
> # Date.pm
> grammar Date;
> my $date;
> rule date_rule { $date := }
>
> # uses_date.p6 (hmm.. I wonder what a nice extension would be...)
> use Date;
> my $date
On Mon, 2002-09-09 at 15:12, Luke Palmer wrote:
> > Going back to patterns, this gives us an added bonus. It not only
> > explains the behavior of hypotheticals, but also of subexpression
> > placeholders, which are created when the pattern returns:
[...]
> > I think this is a very clean and simp
> I'm talking about just in the same namespace, how
> do we keep rules from messing with file-scoped
> (or any-scoped, for that matter) lexicals or globals.
> How do we get rule- or closure-scoped lexicals
> that are put into $0?
How about something like the following rework of
the capture/hypoth
Luke Palmer fretted:
> This is terrible. Calling foo which calls bar mysteriously overwrites
> $date? "Why is $date changing?" the programmer asks. He does an
> exhaustive search through his code and finally says "ohh," and has to
> change all references to the inner $date to something
