Re: (jeffa) Re: Why are closures cool, continued?

That's a good example of using code refs, but it's not a closure. There are no private variables (unless I missed something there).

[dws]

That's a good example of using code refs, but it's not a closure. There are no private variables (unless I missed something there).

The anonymous routine (blessed or not) refers to a lexically-scoped variable in its enclosing scope. That lexically-scoped variable is magically kept alive (in the anonymous subroutine) after that enclosing scope has been exited. That is what makes an anonymous subroutine a closure.

sub makeAnonymousSub {
    sub { print "I am not a closure\n" }
}

sub makeClosure {
    my $x = shift;
    sub { print "I keep $x alive, thus I'm a closure\n" }
}


Update: This is in agreement with perrin, btw. I'm just filling in some details...

[perrin]

Are we looking at the same thing? The example jeffa posted has this anonymous routine in it:

print $foo->print_me(sub {ucfirst shift}), "\n";

It's not a closure.

[mr.dunstan]

Hey! I was thinking something along those lines, just because the variables themselves are not declared -within- the closure ... only near it?

I am thinking this means:
1) There is no spoon, I mean closure.
2) That's a closure, but not an academic example of a closure.
3) Mr. Dunstan, you are mincing words to gain karma.

Zuh? -mr.dunstan

[perrin]

Sort of. To make a closure, you have to refer to lexical variables that are declared outside of the scope of the current sub. That's the definition of a closure.