in reply to Re: Accessing lexicals in other scopes dynamically by name
in thread Accessing lexicals in other scopes dynamically by name

> It would be a bit silly if one couldn't do

Sure ... but...

> Note: Subs only capture variables it knows it will need.

which was exactly my intuition, you understand my confusion, since

my enclosed sub from the OP:

 $getset=sub  {
    my ($name,$val)=@_;
    eval('$'.$name."='".$val."'"); # I can access any variable in this
+ scope
  };

[download]

doesn't know it will need to capture $x!

So whats happening here?

Cheers Rolf

Replies are listed 'Best First'.
Re^3: Accessing lexicals in other scopes dynamically by name
by ikegami (Patriarch) on Jul 30, 2010 at 16:54 UTC
    You never captured $x. It was simply still in scope. You basically did 
    my $x="global";
my $test=sub {
  my $x="pre";
   
  alert($x);           # pre

    my ($name,$val)=@_;
    eval('$'.$name."='".$val."'");

  alert($x);           # post
}

    [download]
    which we've already established should work. Call the sub from outside the scope in which $x resides and you'll see it fail.
[reply]
[d/l]
      >Call the sub from outside the scope in which $x resides and you'll see it fail.

      please define your understanding of "capture" and "scope" (dynamic or static).

      Cheers Rolf

[reply]
        Capturing preserves a variable beyond the end of its normal scope. 
        sub make_closure {
   my ($x) = @_;
   return sub { $x };
}

my $c1 = make_closure("a");
my $c2 = make_closure("b");

say $c1->();  # a
say $c2->();  # b

        [download]

        The $x from the first call to make_closure and the $x from the second call to make_closure are kept alive beyond the end of their normal scope (the end of that call to make_closure).

[reply]
[d/l]
Re^3: Accessing lexicals in other scopes dynamically by name
by LanX (Saint) on Jul 30, 2010 at 16:43 UTC
    Some changes to your code to make it clearer!

    use strict;
use warnings;
 
my $n="outer";
 
my $f;
 
{
  my $n="ok";
  $f=sub { eval "".shift };
  check();               #  "ok"
};
 
sub check {
  print $f->('$n')
}
 
print $n;                   # "outer"
 
exit;

    [download]

    Cheers Rolf

[reply]
[d/l]

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