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Postings from November 2010
On Tue, Nov 30, 2010 at 12:37 PM, Reini Urban <rurban@x-ray.at> wrote:
> Sorry, I don't understand that special theory of yours.
> Why on earth should
>
> BEGIN{my $x = 5; *foo = sub(){$x}; $x=6} print foo'
> ever print 6 again?
>
> We are using lexical scope, not dynamic scope.
> With dynamic scoping, i.e. local $x = 5; you could justify a 6.
>
Closures capture variables, not values. (At least in Perl. I don't know
about elsewhere.) The variable can freely be changed.
Given the following body of code,
{
set(123);
say(get());
}
Observe the differences depending on how those functions are defined.
BEGIN { # Works
my $private;
sub get() { $private }
sub set($) { $private = $_[0]; }
}
BEGIN { # Doesn't work
my $private;
*get = sub() { $private };
*set = sub($) { $private = $_[0]; };
}
BEGIN { # Works
my $private;
*get = sub { $private };
*set = sub($) { $private = $_[0]; };
}
This has nothing to do with dynamic scope. Dynamic scoping would allow get()
and set() to see a variable that resides their caller.
- Eric
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