On Thursday 06 September 2001 08:53 am, Dave Mitchell wrote:
> But surely %MY:: allows you to access/manipulate variables that are in
> scope, not just variables are defined in the current scope, ie
>
> my $x = 100;
> {
> print $MY::{'$x'};
> }
>
> I would expect that to print 100, not 'undef'. Are your expectations
> different?
Yes. I would expect that to print 'undef'. '$x' doesn't exist as a key in
%MY::
>
> I think any further discussion hinges on that.
Yes. My expectations are different. My expectations are exactly like my
previous PATH example.
my $x = 100;
{
$MY::{'$x'} = 200; # Equivalent to 'my $x = 200'
print $x;
}
print $x;
That should print 200, and 100, should it not?
You are creating a lexical in the current scope, and assigning it the value
of 200. You are not finding a currently existing $x and assigning it the
value of 200, resulting in 200 / 200.
But let's be a little more pragmatic about it, shall we? Look beyond the
fire and brimstone for a moment. As Dan said, we can already screw up your
entire world. So other than a couple clever hacks from Damian, how will
they be used?
Generically speaking, modules aren't going to be running amok and making a
mess of your current lexical scope - they'll be introducing, possibily
repointing, and then possibly deleting specific symbols out of that scope's
symbol table. Very precise actions - not random reassignment of values from
hither and yon. Furthermore, unlike the value determination of a variable,
which meanders through the various scopes looking for the most applicable
target, %MY:: table manipulation is a singular entity, and needs to be
treated as such. You certainly don't want to be targetting random scopes
'n' levels up. You know exactly which level you need control over - 99% of
the time, the immediate parent - and that is where any change should be
limited too.
Believe it or not, this feature is designed to reduce action at a distance -
why would we want to create even more?
my $x = 100;
{
use some_pragma; # Introduces some $x
foo($x);
bar($x);
}
# The original pragma's scope has ended... why should we be using the
# same $x? We shouldn't. The $x was created in the inner scope, and
# we're back to ours
%MY:: access the pad, not the variable.
--
Bryan C. Warnock
[EMAIL PROTECTED]
