I'm sorry, I think that I've given offence. None was meant.
Code that doesn't compile (under strict) is what you meant? And it is your STORE that causes things to "blow up". Just to be clear, my code works just fine if given a tied implementation that isn't seriously broken.
The
$class, you mean? Yes, that was a silly think-o—sorry. It seems to compile fine with the obvious modification, though.
My point really was just that throwing a maliciously tied variable at your implementation could break it (a non-point, now that I see that the same is true of local), and I was looking for code that was completely oblivious to the actual variable it was localising.
Did you get such an error from Perl when running my code?
Yes, I did, running perl 5.8.9 installed on a Mac via MacPorts. It also makes sense to me by visual inspection (although you are rightly sceptical of my ability to execute code by looking at it):
tie my $x, 'Tie', 1 will leave
$x tied to
\1, and de-referencing that will lead to an assignment like
1 = 2.
Of course, I could just put my $temp = $x; $x = 2 at the top of the scope and $x = $temp at the end ... but this isn't completely satisfactory: For example, if $x starts off tied, then it will no longer be after my $temp = $x; $x = $temp.
You are wrong there as well. my $temp= $x; $x= $temp; doesn't leave $x no longer tied.
Yes, you are right that I am wrong! :-) I assumed that it would destroy
tiedness, but (wrongly) didn't test it. What I was thinking—and this
is true—is that
tied variables don't always survive round trips, in the sense that
my $temp = $x; $x = $temp need not leave the value of
$x unchanged. (Perhaps a condition on a reasonable implementation of a
tied variable is that that doesn't happen, but I think
it's true of a lot of existing classes do not satisfy this condition.)
Yes, local causes a variable to temporarily not be tied (something that I find mostly to be an accident of implementation choice not something that makes sense as an intentional feature)
This is not true on my Perl:
sub TIESCALAR { bless \my $o => $_[0] }
sub FETCH { print "Tied\n" }
sub STORE {}
tie our $x => 'main';
{
local $x;
$x; # => Tied
}
What
does ‘work’ (for my definition of working!) is going the other way:
our $x;
{
local $x;
tie $x => 'main';
}
$x; # nothing (except a warning about void context)
