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Re: Throwing lexicals
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From:
Luke Palmer
Date:
September 9, 2002 13:14
Subject:
Re: Throwing lexicals
Message ID:
Pine.LNX.4.33.0209091401520.6817-100000@babylonia.flatirons.org
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 := <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 is no way to use someone else's grammar and prevent it
> trashing your namespace.
Err.. I don't think so.
# Date.pm
grammar Date;
my $date;
rule date_rule { $date := <something> }
# uses_date.p6 (hmm.. I wonder what a nice extension would be...)
use Date;
my $date;
m/ <Date::date_rule> /;
This would mess with $Date::date, not $main::date. If there was no
$Date::date, it wouldn't mess with anything, and it would store
the return value of <something> in $0{date}.
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?
Which of these are legal, and would provide a solution?
/ <something> { let my $date = $something } /
/ <something> { $0{date} = $something } /
If either, I guess I have no complaints. I'll be angry if the latter
isn't legal. Still, they seem a little bit hack-like....
Luke
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